Budget 318 build

Sorry, all I see when you break it down to the nitty gritty is head work and/or swap.

On the as cheap as possible I’d just do the 360 heads and cam according. To further push performance, converter and gear. While not exactly cheap, it is the next logical and best step unless you get a Super Charger. The super charger store or a torquestorm. Add appropriate ignition parts and let it rip! 5-7 pounds of boost does wonders. Bang for the buck is inexpensive in the big picture.

Ok ok ok, yea, the price of parts is skyrocketing!
So is your performance!

Bottom line. You can not exceed the speed of your wallet thickness. Do the best with what ya got until another day.