318 2bbl Rebuild

+1 to @318willrun suggestions.

i'd recommend a throwing in a 360 2bbl cam (or something similar) while you're there-- you can have yours re-ground and the lifters refaced.

but beyond a good timing set, fresh oil pump (and pick up!), hardened exhaust seats and having the heads gone thru it's hard to say what else you might be looking at until you get the motor open.

hope for minimal wear and you can get away with a re-ring-- the early motors already had decent compression. but if you need to go next over, there's tons of options piston wise for what you're trying to do. how spicy you wanna get (*cough* lighter pistons *pistons*) really depends on budget.

ETA: on the duals, get with TTI. they sell a complete kit from head pipes to exhaust tips and the fit is absolutely spot on.
360-2bbl cam
I've used a couple of those in 318s that are driven regularly. It will be a noticeable improvement, by seat if the pants. You want a melling SPD 25.

Also... That cam is IDENTICAL to a COMP 252... I trust melling over comp these days. Good chance to find some old stock somewhere. Only difference is 0.015 less lift of the 360-2bbl cam vs the comp. Not enough to notice. The rest of the specs between these 2 cams are dead nuts IDENTICAL.
Only difference I've seen is in price. I've been able to find the spd25, first in a hole in the wall parts warehouse in Chicago (can't remember name or address as that one has been too many years ago, I drove down and bought it over the counter) the 2nd was eBay. But the melling is like 1/4-1/3 of the cost of the COMP version.