As Cab says, the 400 block is your winner. I have a 512 & a 455 stroker 400, both are as good as each other although I rev the the 455 higher. If you go past 470 cubes you'll want to consider max wedge ports if you want to make real power, but a 500+ cube std port would make a zippy street car, just the top end will be lacking, but how often are you going to be maxed out on your rpm? I don't use Source parts, im a believer that you don't skimp on the spinning bits, if they fail, the costs are astronomical & it would have been cheaper to have bought real quality in the first place.