W cobra mani and heads maybe 250 at motor maybe 300 but I doubt it. Read an article awhile back in muscle stangs n fast fords I believe it was about bolt on horses n they put gt40 (cobra) heads on and the dyno showed 27 hp gain at the rear. They spent something like $3k worth of bolt on stuff labor not included and gained 80 some odd horses at the tire. I'm w you about being leary bout buying junk motor I'm also leery bout buying used parts like heads, supercharges, etc, especially sight unseen via the web. People who are using trickflows top end kit are putting down like 270-300 hp. That kit runs in the 3k range and I don't believe it comes w rockers. As for the tune up to add to what the others recommend I'd also get sum Mass air cleanerI don't want some junked explorer engine though I would feel more comfortable rebuilding for 2k and starting from there possibly save enough to get the h/c/I done while its apart. What kind of power would I put out with a cobra manifold and gt40 heads?