What Jake said. New guides, seals and a good valve job and you are good to go. With your cubes I would have someone like Modern Cylinder Heads do a CNC port job also. That is the setup on my 528 and I am happy with it.  I have the MP heads on my 572...mid 9s on motor at 3800+ lbs. Send your heads to MCH and have them replace the guides and CNC port them. 
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
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