Why not buy some heads that will work on a 500" stroker, but put them on the current 440, and let it run what it runs. If it isn't enough for you, build another stroker shortblock while you spray the old one. twocents

CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax