Uhh...Anyone else running hydroboost???

[Tdubbyount]

Ive got a 79 k10 swb that came factory with hydroboost brakes (came w/ 5.7 olds diesel) and the brake booster needs replaced...But im having a little trouble finding the correct one. Niether Napa or Orielly's had the part listed under my truck, so i came up with a part number for a '79 and had one ordered. However, it wont work. As you see in the picture, the new one came without the piston spring and baffle and spring retainer, so i pulled it out and tried to re install it on the new unit, but there was a substantial bore size difference between the two. Like 3/8 of an inch. Makes no sense. How many different units are there? Anyway...I have a different one on the way, no clue if it will work, i just found one that had a different part number. So we'll see. I'll try to get more pics up. Any help is appreciated