I use the copper colored RTV silicone on copper head gaskets w/ O-rings. Put a light coating on the gasket, assemble, and let it sit for at least 24 hours. Never had a problem.
Done this on our 436" sb chevy w/ 14.5:1 compression.

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