Engine/Tranny from 87 to 85???

[Alaskan85K5]

Hey guys I may have a lead on a 1987 GMC K5 that's getting parted out. What kind of problems would I run in to if I took the 87 Engine (TBI) and Tranny (th700). And replaced my 305, th350.

What else might I like out of the 87 for my 85?? Also what should I pay for the engine and tranny?? Thanks for any info!!!

 

[dyeager535]

Two piece/one piece rear main issue, different valve covers, but if you get the whole engine/transmission, shouldn't be anything serious. Maybe t-case and drivelines, but I don't follow the 208/241 stuff close enough to know for sure.