318
For a mild 318 use the following: a stock 340 cam and matching springs, or the summit racing milder perf cam and springs, double roller timing chain, dual plane 4 bbl intake like the edelbrock performer, a small 4 bbl like a 600 cfm carter/edelbrock afb or a holley vac secondary carb. For the exhaust you could add duals to the stock exh manifolds, this would be best done at a local exh shop, and some turbo mufflers.
Assuming you want to do this on the cheap this would be the way I'd go. I'd start attending mopar swap meets and shows to pick up this stuff used, except the cam, lifters, timing chain and springs - buy new stuff.
I'd also recurve the distributor for faster mechanical advance. Should be a fun ride once done.
Next step would be headers, higher axle ratio, and better cylinder heads, but assuming you arent there yet - start with the above suggestions.
Enjoy !