Methanol rules :bigthumbsup
I also suggest a 363 for a high hp street build. 0.125 oversized pistons with small block heads, inject meth and blow through it all! Easier said then done right?
I was considering the same but with a 427 with 0.125'' oversized pistons. Changed my mind, the 363 has better rod angles, and when your blowing through a motor building it strong is more important then pulling cubes. If you build it strong enough you can push crazy boost numbers and make the same CFM as a big block with low boost.. I would start with an aftermarket 351W block, capable of housing 1000+hp and capable of being bored SAFELY (recommended by manufacterer) out to 4.125''. I just got my Dart SHP 351W in and im starting a high hp build as well. The block is reasonably priced considering its capabilities. It could be bored and strokes to about 440 something c.i. within manufactuers recommendations of max bore and stroke. That is just your window of oppourtunity using that block. Max specs are like 4.185'' pistons 4.250'' stroke. If you search up those blocks you will read nothing but good feedback. You will also read alot of people pushing the block past its recommended power rating and it manages to hold together.