Have you considered a 6.2L? Compared to the 4BT, they're a lot less noisy, lighter and not nearly as tall so it'll fit in the engine bay a lot easier. I've heard too many complaints about noise and shakes with the 4BT.
1990 ¾ ton 4x4 Chevy Suburban
-Cummins Diesel - 12 valve - factory rebuilt
-6 speed bullet proof manual transmission - NV5600
-Gear Vendors Overdrive
-Upgraded Holset HX-35 turbo
-NP205 iron transfer case
-3.73 gears
1982 ½ ton Chevy Suburban
-6.2L diesel - high nickle crack free 1982 block
-Stans headers
-Ported heads
-Timing gear
-4 speed automatic
-3.08 gears
-30 mpg on freeway