I went with a bb for the higher HP capability (as far as OEM blocks are concerned). I think I would do a sb for a big single, or do twins next time for fitment issues.

'72 Scamp, 3500#, 440, S400, blowthrough, meth. inj. 9.78 @ 139 so far at 12 psi, 11.00 @ 131 on real street tires.