My truck date is 2/99. Would I need AD's or AB's? I read something about if it was built before or after the date of 12/27/98. Is there another way to verify what I need without pulling the valve cover? Thanks again.

 

Cyl #'s 1-7 will be AD. Cyl# 8 may also be AD, or it may have already been changed in the past to an AE (so called "long lead"), to cure a "cackle" complaint due to design flaws in the oem fuel system.
IF it has been swapped to the AE in cyl 8, then the ecm would have been flashed at the same time. If so, you would need to use the AE. If has not, then you need to stay with the AD. You would need to pull the driver's side valve cover to check.

Alternatively, you could just go ahead and upgrade to 160cc or 180cc single shots. This style of injector is said to have better fuel economy than the stock "split shot" injectors, as well as being "easier" on the HPOP. Of course, they can also make more power, depending on the tune. Speaking of which, a custom tune/chip is required if you do make this injector swap.

I just bought mine from Full Force Diesel:
7.3 Powerstroke Stage 1 Performance Injectors