Blue pill or red pill = 675 or 920

920 heads are great. But, I would have them tanked and magnefluxed first. If good, milled .020, mill the intake side .019, probably need to replace the exhaust valves (stainless steel), clean up the bowls, get a competition valve job, brass freeze plugs, and redo the guides, might as well add 340 valve springs (or equivalent) while you are at it, and use Fepro Viton valve seals. On the cheap, leave the heads on until the next problem occurs, then slap on your "done" 675's. You can also get a set of 360 heads and do the same routine. A good cam would be nice... See how it goes? Now about that 7 1/4 rear...