swapping parts

[jd4300fel]

Not sure what group to put this in but since it's going to land into a 72 camper special I figure i would start here. Mods please feel free to move if needed.
after some issue's with my 400 bb, I am going to swap it out for a 350 crate
motor that has low miles one less than a few hundred. I have heard the truck with the donor motor run. and for the 2 grand I feel it's a good deal. the donot vehicle that is a 1976 chevy C10 with a 350/350 combo (although originaly it says it had a 400 in it) with 4 wheel drive currently running 35's.
danna 12 bolt 6 lug
The truck that it's going into is a 72 chevy custom camper c20 400/400.
dana 12 bolt 8 lug. I am going to swap out the engine. what else is worth
going after. tranny, rear end ?
My plans for the truck are to make it a driver that I can drive to and put inthe local small shows mostly drive it and have fun. looking t doing a lower kit 4/6 ece. move the fuel tank to the frame.

On the the engine I noticed a couple of things first the TV cable( the cable that connect from the carb to the tranny ) is not connected, and second in the middle of the intake manifold the paint looks like it burnt off right in the middle of the carb location buy the head on both side Is this normal the engine has headers and edelbrock carb and manifold ?

An suggestions are greatly appreciated.

Mike