The only advantage of using the 429 shaft is that the engine will RPM a bit quicker, but the trade off is giving away a bunch of torque that the longer 460 shaft will develop... If you want even more power, the go with a stroker kit and you can go as far as 557 cubes out of a 460 block. Factory 460 blocks are all about equal, depending on how big a shot you're planning to run out of the bottle you might want to consider going to the 4 bolt splayed main caps... We've ran BBF's drag racing for years, and IMO the only thing better then a lot of cubic inches is even more cubic inches!!!!