Need advice on my 318

275 hp can be attained without replacing pistons. Really, just a 4bbl (600 cfm), dual plane intake (I like the Weiand action plus), a cam with about .450 lift and 268-270 advertised duration (try for a 112 or 114 centerline), and of course dual exhaust. If you really want to be sure, go headers or better manifolds. Tune it well (timing, jetting). If you have any extra money, work on the heads (open bowl area, intake ports where the intake mates, maybe even larger valves...).