A couple of things I'd want to know before going much further.....why are the door and fender not there? Wrecked? Unibody ok? Does he know where the original engine/trans went? Look on the pink slip for the VIN. No pink? I'd be real careful and check every VIN stamping I could find.
If your oil pressure is fine before the swap, the cam bearings are probably ok. They're a real pain to do with the engine in the car. Just be careful when you pull the old cam and when installing the new one that you don't damage the bearings. They're easy to nick. You haven't said which engine...
What do you have for an exhaust system? If it's the stock 318 manifolds, that can cause a big bog on acceleration. On the brake issue, we need to know what the actual intake vacuum reading is before doing anything. It's a good indicator on what might be your hesitation problem too. I'd run a...
You need to include the sending unit, voltage limiter, and wiring harness in your calibration attempt. Those other items will effect the resistance in the circuit and therefor the calibration.
Keep in mind that the swap will require the proper oil pan and torque converter/flywheel. The converter/flywheel won't interchange between the two engines unless the 360 has been internally balanced. The pan won't swap at all....end seal size is different.
I don't see the grille listed on the Year One site. They have the '70 grille and the '72-4 Challenger grille but I don't see the '72-4 Barracuda listed. Do you know what page it's on?
Thanks, Mark