Cheap 318 performance mods.

In my experience nothing "performance" Is ever cheap. Its a never ending rabbit (money) hole. I started off similar to you was going to take an 80s 318 and clean it up regasket it add a small cam a 4 bbl intake headers etc. Well I pulled the heads to find that it needed to be overbored pulled the cam it needed new cam bearings. The heads needed a valve job due to worn seats etc etc. So I figured since I needed all this machine work I'd step up and build a 360 instead. About 3 grand later my budget was blown and I had one heck of a stout 360 lol. Long story I know. Sorry. But if you can get away with it and you have a good 318 core that doesn't need new pistons or worn cylinder walls (unlikely) I would get a small cam, a four barrel intake I'm a fan of the factory 4bbl spread bore with a thermoquad on top. And a set of magnum manifolds from a 5.2 mag. If the 318 is worn out and need machine work. I'd follow some advice I got from here and never followed, I'd find a 5.2 or 5.9 mag in a junkyard or marketplace and start with it. Speedmaster has a good intake for the mag heads.