If you rebuild the Cast Iron Heads 'properly' ?
ie: Hone-Fit Bronze Guides, and with new Valves/V-Springs/Retainers/Locks/Seals etc., etc., imo... you will probably spend the same as just buying STEALTH Heads
albeit,
there will be NO room $-wise for Porting the Cast Iron Heads... which will most probably Flow in the 230'ish cfm range @ .600" Lift at best ?
whereas...
the Stealth's are 260'ish OOTB as delivered.
Meaning....
those rebuilt 'properly' Cast Iron Heads are best utilized targeting a 460hp build(230 cfm X 2).... and have a HIGH detonation probability(open Chamber / poor quench) on 91 Octane pump gas.
whereas...
as delivered... the STEALTH Heads for the same Money are at least a minimum 50 hp better than those Irons in any application, and have closed Chambers for far superior quench characteristic on pump gas.
Your call.... but why would you spend the same to have LESS ?