70 D100

I would go 440 and get a big block bellhousing for the existing transmission, but I like a 435. You mentioned the bell housing bolts. IIRC, have to drop out the clutch and flywheel and the bolts are inside, gearwrench is your best friend! That’s the way the 11 inch clutch has to go behind the six, being the 11 inch flywheel starter gear ring is larger than the bellhousing bolt pattern of the \6. I took the four bell housing to transmission bolts loose and left the transmission in when I swapped engines. I advise lining the clutch up with the input out of an old transmission instead of the plastic garbage that comes in the clutch kit, putting it back in with the bellhousing on makes things tricky. With a V8, bolts are outside the housing up to a 12 inch clutch.