300 HP out of a 318, is it possible with bolt ons?

To me bolt on is anything that you can bolt on a basic short block (block + rotating assembly)
Which are the parts that are responsible for the vast majority of the power, which is why I don't get the naysayers to bolt on power. The question in this application is how much power is available with stock 318 heads about 175 cfm, with a lot cam an cr should be able to get 350+ hp but with stock cr and a streetable cam should do alright, even if it falls a bit short of 300 hp I'm sure the OP will be ok with it. 300 hp is probably around a 230 cam with stock cr which is on the high side unless going with deep gears and stall, I'd stick around 215.