Slant six or v8 swap for use in a truck

I had a 63 engine once to replace a blown engine in an f body back in late 80s. . I found out the hard way about the early/late torque converter mismatch.
I rebuilt that 63 engine and had to take the crank out of the bad engine (also wasn't the original engine from the car) and have the bad engines crank machined to put in that 63 block to make things work