Really not to much holding you back untill you split the block........This question really has no answer. You might make 650hp @ 20psi but it will only last for a short time, you know what I'm sayin?
it depends on how much money you have, what block,internals,heads,cam,intake, everything depends but i have seen a N/A 302 get to 550 HP (14:1 CP, nasty a$$ cam). So i really have no idea what a turbo could do for one. But you really need to specify the question a little more because it could probly range into the 1000's
i guess why i'm asking is because i don't see the purpose of stroking to 306? if you can do the same with 302 and put the stroker kit money else where.
A 306 is not a stroker. Like everyone else said, the block is the weak link. A 302 with a hefty amount of boost can be pretty nasty but once you start to get above 450 rwhp or so your sitting on a bomb basicly. Can a stock block 302 make 650 horse? Yes it can. Will it last? No it wont.