300 HP out of a 318, is it possible with bolt ons?
Regarding the OPs question, this reply from MOPAROFFICIAL will get it done.
I think Mopar wasn't paying attention to the OP post.
He (the OP)has the Eddy 318 intake with the small 318 sized intake ports and the LA bolt pattern,
Magnum heads are neither a simple bolt on for his build nor would they make 300hp on a 318 with the 340 cam.
OP'd have to spend over $1,400 to switch over to magnum heads.
There is a very slim chance in getting 300hp out of a stock 318 with just out of the box parts (bolt ons) or did he (the OP) mean the car Magazine definition of bolt ons?
IE-Real bolt on- stock $400 rebuilt 302 casting heads, with 3 angle and resurfaced as they come from the machinists.
IE-Magazine bolt on-$3000 heads with $2000 of machine work which are shaved and decked,fully ported, edelbrocks ,cut for bigger ,back faced and deshrouded valves with shaved guides and a 5 angle valve job.
It takes a lot of reworking and customizing of parts to get 300HP from a 318.
It's no longer a 318 if it's been bored or stroked.
I didn't suggest cnc'd aluminum heads because he be spending 2/3 of buying a 310 hp 400ft/lbs 5.9 crate engine for a little more than the heads cost and swap most of his LA parts over.