Most out of a built block and sticking with the SC? You have to go air to air. Just don't ask Jwillis about it.
The way I see it is this:
1. Built block + stillen oem = 400whp (cheapest)
2. Built block + stillen a2a = 525whp? (extra 2k? and not sure sasha will do this)
3. Built block + BP kit (most affordable) = 700whp (extra 8K)
So what are your power goals?
Also, what are your current mods? Supporting over 500whp is a lot different than supporting 400.