VC-3-B is Motorcraft Orange Coolant that is specified for your 6.7L. But you can use any coolant meeting Ford's WSS-M97B44-D Specification. Most coolant suppliers will have that available.
VC-7 is Motorcraft Gold, which is not specified for your diesel.
Here's a Ford document that lists all the coolants, but it's a little confusing to me. But go by your owner's manual, specifically the Diesel Supplement.
klhansen - Thank you for that reply but that did not answer the question I asked. I have already found that VC-13 is the replacement for VC-3 but I went with the yellow coolant from O'Rielly as it met the specs for ford.
No idea what the letters mean - likely just something that someone at Ford dreamed up. Maybe VC = Vehicle Coolant? The last one is likely an upgrade sequence, B being the second change to that VC-3 coolant and G being the seventh change to VC-7.