is heat soak your only reason for not likeing the headers? if so there are other remedies to fix that... i have headers on all my cars & none have heat soak issues. replacement oem type starters can be crappy quality out of the box, so they will benefit from a heat shield or heat wrap product. also too much advance timing can be a major contributor to hard starting when hot. check timing or try a heat shield before condeming the headers.
a 2nd option that is much less work than swapping out the headers is a mini starter, they are cheap & will usually cure any stock starter issues, i run a summit brand mini on my 11:1 stroker motor with BIG round tube hooker super comps, the tubes come within 1" of the starter & it has never showed the slightest sign of heat soak issues.
as for your question, on a mostly stock engine you wont lose too much power changing to a ram air style manifold, but going back to stock logs will be a more substantial loss, but again for a stock engine hard to say how much.. maybe 20-25hp? i would definitely look into the starter itself first or try to protect it from the heat before swapping out the headers... ram air manifolds are not cheap!
