Help! I want to build my block???

Either of those will do. It just depends on your power goals. When in doubt, do Dart.

Theoretically, the Dart and World Products blocks are better, but I've never heard of anyone breaking an R302 or an A4. So if you have access to one for a fair deal, then do it.

I'm guessing that you already know it, but the way you worded your post was kinda funny. You will not necessarily pick up 100 hp just by changing your internals. Adding displacement or RPM will pick up power if the blower stays at an efficient flow rate. Keeping the same displacement and powerband with a stronger block and stronger parts will not pick up any noticeable power.

Chris

If you are looking into aftermarket blocks, consider moving up to a 351 block.

its cheaper and will take 500-700rwhp unlike the 302 block.