Hello to Allpar's from Cajun Country! Bought a 1987 long bed slant 6. Blown motor. Thinking "waring Will Robinson" I could put my 440/727tranny in it. What in the world will I have to DO? To spin the tires.
Welcome to the forum. Given you don't have smog requirements to worry about, you will need the motor and transmission (slant six trans is different), motor mounts, which can be sourced from Schumacher, they have a kit for that, You will need to redo the exhaust, and redo some wiring. Now there is a little bit to do, if not mistaken, about the exhaust manifolds, I think the truck manifolds are different, dump in a different place to clear the frame rails, best to check into that. Otherwise, it is a popular swap and quite fun. Double check the rear end you have, make sure it is going to be able to handle the extra power and tire spinning.
I think that the frames are basically the same regardless of the motor. I'd spec out motor mounts from the last year of a big block in the truck and if there aren't holes in the bolt-down plates, just drill 'em...
Well, if your 440 is an RV transmission, that's a new one, it would be some other than Mopar transmission but some kind of industrial or commercial transmission. Either get the proper big block (383 thru 440) transmission and tailshaft yoke, and have the driveline redone to fit.