square 4x4 bellhousing location 250 vs SBC

[D13]

I have long wanted a 4x4 square body. i want a long bed 3/4 ton (I use my trucks as, well, trucks) (plus I likethe look of tall tires on steelies with hubcaps). Prefer automatics but not desperately (grew up on 3 on the column). I prefer GMC's (always have!) and have lots of parts including a couple driving 2wd trucks plus a nice cab and clip.

I really like my straight six's, have 5 of them including a driver and a fresh lower rebuild with a compression bump and cam.

So here's my dilema. There is a decent 86? 3/4 4x4 chassis with a rusty body on it for sale locally. I'd like to swap in a 250. I'm pretty sure that the truck is 350 / TH400. My big issue is whether or not the bell housing face is in the same location. Anyone out there done the reverse swap and can tell me?