there is no way in hell a stock engine is gona handle ported head with a blower for very long. unless you were running ported heads with stock cams and around 8lbs of boost on a centri and 6lbs on a KB. keep in mind that the stock engine gets sketchy after 400rwhp. I would pull the engine put some h-beam rods and good forged pistons before even considering a combo like that.
I would check out the modular depot section "My ETs" and I'm sure some guys have some numbers. They are actually ported truck heads.
As long as you don't get greedy with pulley swaps, a stock block will be fine. The best way to make power is removing restrictions like heads cams and exhaust and then bring the boost back up to a safe level since those mods will reduce boost. Ported heads will lower compression too. A great and safe tune is a must. Its when people stock everything with a s/c and add boost only that engines give in, or thats just my opinion.