I'll address the OC first. The Bulletproof OC is IMO a solution in search of a problem. There is absolutely nothing wrong with the OEM Ford OC. The issue related to the OC is the Ford gold coolant that is full of silicates and when it oxidizes the silicates precipitate out and combine with leftover casting sand in the cooling system to create goo that clogs the tiny passages in the OC leading to failure of the OC because it cannot reject enough heat from the oil through the goo.
Once the gold coolant is gone and the system has a coolant filter installed there is no reason not to use an OEM OC, because the root cause of OC failure has been removed. FYI, IH, who designed and built the 6.0, had a coolant filter on the engine when delivered to Ford. Ford chose to eliminate it to save a couple dollars per truck.
The BPD kit goes to an external OC. Its quite expensive, and there have been several issues reported by those with this kit installed. Cold weather is an issue for this system and it can overcool the oil. Ideally you want that oil to be in the 200-220 degree range. The oil is too thick below that temperature, but because the external cooler is down in the ambient air, not insulated inside the engine, it has a tendency to keep the oil temperatures too low when it is cold outside. The other issue I've read about is a spike in temperature after coming to a stop while pulling a load, so much so that guys are running dedicated tuning to trigger the cooling fan for the engine off of oil temperature. To me, for a kit that costs $2,500 to have issues like this is utterly unacceptable. Its marketed as a cure, but it seems the cure is worse than the disease.
The next question is do you want an EGR delete or a BPD EGR cooler. To remain emissions legal you have to keep the cooler in place. The BPD cooler is the only one I would use, because it has a lifetime warranty and I've yet to hear of a failure. Personally, I'd rather ditch the EGR cooler completely and eliminate the complexity. But, some people that live in certain states like CA for example don't have this ability because they will fail emissions. Here in DE there is no emissions testing on vehicles in excess of 8,600 lbs. GWVR, so its not a concern for me. The cooler not being in place and the system not being functional will not cause you to fail emissions (unless you have an '06-up where you might get a CEL, but that can be turned off with a tuner too) because the system doesn't work at idle. So the only concern becomes a visual check, and even in states that have that I'm betting CA is the only state where they know to look for that cooler. Ultimately its up to you, but now you're informed.
On the FICM, just send it to FICMRepair.com - FORD Powerstroke 6.0 FICM Repair, PHP Tuning and Truck Parts
while the truck is down regardless of whether or not is "tests" good. I put that in quotes because no one can really test an FICM. All they can do is check voltage, which only tells you that the capacitors in the amplifier are good. Plenty of FICMs have been bad and showed good voltage. FICM Repair can actually go through the FICM and replace all the failure prone parts and then send you back a unit that has a lifetime warranty (if you chose that option). Your reward will be an FICM that will never fail, much better cold starts, and if you opt for the Atlas 40 tune (which I highly recommend) you will get better throttle response and possibly even better mileage. DO NOT get conned into one of those 52 or 58V FICMs. They have a high failure rate and offer NO performance advantage. Its all marketing hype. There's never been a dyno test showing any gain in power from anything other than the tune run in the FICM, which you can load into a regular 48V FICM and get the same result. But, there have been a lot of salty 6.0 owners who had one of those high volt units fail and the company that sold it telling them the FICM is fine and its something else when its not. I don't think I've ever heard one case of any company making good on their failed product. The issue is heat. A lot of FICMs fail from heat, and they are only 48V. When the voltage is increased it means more capacitors, and thus more heat, but the heat sink area that is designed to remove the heat is the same size. Just not worth it, walk away.
As for the other parts, I prefer all OEM parts. In particular I would NEVER use head gaskets other than OEM. There were a rash of failures on studded 6.0s that traced back to the aftermarket gaskets (Black Onyx (isn't all onyx black? should have been a tipoff right there)). There have since been other gaskets like Black Diamond, etc. that seem to have a good track record, but to me its just not worth the risk to save a few dollars on a job costing several thousand dollars. Definitely use the ARP studs and follow their installation instructions to the letter (buy extra ARP lube the small pouch in the kit is never enough).
On the heads, what you want is for them to go to a machine shop and be Magnafluxed for cracks, especially in the area of the exhaust valves and the injector bores, which is where 6.0 heads tend to crack. If they pass that then they need to be milled perfectly flat. Keep in mind you can only mill about 0.008" off a 6.0 head. You must maintain a minimum distance of 3.740" from the valve cover rail to the fire deck, otherwise you will have valvetrain geometry problems, and risk getting a piston too close to a valve. Its also a good idea to check the valve seal. Speaking of valvetrain geometry its also a good idea to install the updated pushrods. There have been valvetain issues on some 6.0s, especially after a HG job where the heads were machined, that have been traced back to pushrod length. Ford has issued revised length pushrods to handle this issue, so its a good idea to use them and stave off a potential problem.
On injectors, re-ringing them is the bare minimum. If they have 150k on them or more I would seriously consider replacing them. That's about typical service life. They don't last forever, and typically in the 150k-200k range they will start to develop idle issues and intermittent running issues that trigger no codes and drive you nuts.
Clean the turbo while its off. Typically you should do that every 50-100k to keep the vanes moving smoothly. Also replace your hot side CAC boots. If they've never been replaced they are cracked and likely leaking to some degree. The boots break down from the oil that gets into the intake tract from the crankcase vent. Rerouting that vent is a good idea. I run a BD kit that redirects that crankcase vapor through a filter and collection system that I drain at each oil change. I get about 1/2 pint of oil out of it every 5k, so that means normally 1/4 quart of oil is getting dumped into the intake dirtying up your valves and ruining your CAC boots.
Price wise the quotes you are getting are not out of line. Average cost for a bulletproofing job is $5,500. Some places charge a little less, others a bit more. What would be important to me is that the shop has a good reputation, offers a warranty, and stands behind it. I do all my own work. When I was a kid it was because I didn't have any money to pay someone to do it. As I've gotten older its because I know I won't cut corners, I'll take my time, and I'll be damn sure I got it right. Finding a shop that lives up to my standards would be tough, and they'd likely be pretty expensive.