Quote Originally Posted by Ken1960 View Post
I don't have power brakes but didn't b blocks come out in cars with manual brakes, and I have got the power glide in there now want it hold up to a b block engine it already has heavy springs in front
Ken,
I have no direct experience with the 572 crate engines from Chevrolet Performance, but IMO their engines are a great value. There are thousands of GM 572's out there performing flawlessly, which speaks to the quality of their approach to me. Then again, I'm just a dumb engineer who over thinks everything, so you need to put that into your evaluation, too.

The issue with power brakes is that an engine with a lot of overlap won't pull enough vacuum at idle & certain loads to ensure that the brake booster will have enough "suck" to provide any boost. The solution is to either have a good sized vacuum reservoir with check valves, or even better to have an electric/engine driven vacuum pump to provide a consistent "suck" to your accessories. Manual brakes are not a problem.

Your powerglide, if it's built for the service, will be virtually bulletproof. There were lots of powerglides running in slingshot dragsters pushing big power numbers and lots of traction back in the day. They're crappy for long range cruise efficiency, but hard to beat for play.