You also should check 318willrun videos
https://www.youtube.com/@318willrun/videos and his builds on this site do a search. He has shown a few times the few steps needed to turn a 318 into a decent performer.
If your car already has a good running 318 i'd start with a 4bbl and mild cam swap duals a good tune, 3.23 shift kit and maybe a stall, you'd be surprised how much that would wake up your car and wouldn't even make more than 250-280 hp. If getting heads I'd look into speedmaster there a decent priced aluminum aftermarket head and would add probably 40-60 hp to what i said above.