You say you are undecided on heads, but you want quench... That pretty much eliminates open chamber heads without a bunch of machine work (or domed pistons which have fallen out of favor). A magnum style head (assuming you are not dealing with early HP 340 pistons that are above deck) will let you get quench easier (prevents detonation), and you can then also go with less timing (also prevents detonation). So with quench and less timing, you are greatly increasing your ability to run on 87. Heat builds power in the compression chamber as long as you do not have detonation. Octane has a cooling effect in the chamber, and so helps prevent detonation. But dumping octane in an engine that does not need it can actually reduce power by cooling the chamber more than necessary.