www.classicdieseldesigns.com or www.russrepair.com or www.conestogadiesel.com or find your local pump shop and have the springs in your injectors cleaned and shimmed to match cracking pressure and spray pattern. There's really not much to wear out on these injectors if the fuel filters were changed and clean fuel was used. If they've seen lots of WVO or WMO then they may pretty dirty but otherwise probably just need a tune up and cleaning.
Look at all the flats on the hex part of your injector, there will be a letter(s) stamped on one of the flats. Yours will likely be BB if they are original but Code BB or E or G will be fine for all non turbo applications, but they do need to match. There's a strong argument to be made that a quality rebuild from one of the guys listed above (or some others) is better than a new out of the box injector simply because springs in new injectors will change their rate faster than the old seasoned ones thereby losing cracking pressure. Typically a new set of injectors needs to have the pressures rematched after 10k miles or less whereas the CDD owner has documented much longer intervals with his rebuilt injectors keeping cracking pressures very close across a set.