741 v 742 v 489 housings

I have a chance to get a 741 case and gears (open, 3.23) for $50. Since the pinion is 1.375 in diameter, how much oomph will this take? I have a Aug 70 340 with a six pak combo, pocket ported x-heads that I will use on this. Probably a bigger cam also. Will eventually move to 3.55 gears, but now stay with the 3.23. How much power does this case with that small pinion handle? Thanks.