[Alan Roehrich]

The 350 will cost less, and may be slightly faster. The low gear difference between the 350 (2.52) and the 400 (2.48) is negligible. I don't think I'd bother with a 2.75 low in your car. I'd be more inclined to buy the best converter possible. Of course, you'll be moving your crossmember and changing your driveshaft to accommodate a 350. The converter is the same, but your stall will go down when you put a converter that has been in front of a heavy 400 in front of a light 350. Maybe as much as 200-300 RPM.

I don't think you can make enough power or spin enough RPM to make reliability an issue with the bottom end of an Olds in Stock if it is well built. The stock F0 and F1 block is good to 600+ and 7000RPM (and that's 7000RPM while making good power, not 7000RPM going through the lights well after peak HP has come and gone). The stock cast crank will handle that as well, properly prepared.