Need Help. Converting A V6 Auto To V8 Manual

first does either car have EFI? if not then the swap becomes much easier as all the wiring generally swaps over easily. you might have to extend some wires, but thats easy enough.

the K member doesnt need to be touched as they are the same. the V8 goes in place using stock V8 mounts. the drive shaft might need to be changed as the length may be different though, so look for that. you will need to ultimately upgrade the radiator to handle the heat from the V8, especially if you hop up the V8.

you obviously will need to swap over the pedal support, and punch a hole for the clutch cable.

since you are going carb, its easy enough to make a harness that fits your needs. get a wiring diagram for your V6 car, and one for the V8 car, and work from there. you will see what wires you need and what ones you dont. you might even be able to repurpose wires from the EFI to work with the carb.