Chip,
I'm using an early '60s V8 bellhousing in my swap with a 250 in front of it. I'm setting things up so the carb flange is level front to back and side to side. That should give me the correct drive line angle, but I'll check to be sure and if necessary raise or lower the front of the engine to correct to 1 to 3 degrees.
The late L6 engines are actually slightly shorter than the early L6s, but they are also 150 to 200lbs LIGHTER than the early engines!
best wishes,
Les
