actually, the old LT-1 heads were "492" castings with 2.02 X 1.60 valves. These are still available from GM (new) from places like SDPC2000.com. The old 462's that you mention did not flow that well however. I've seen a couple articles where they were outflowed by 882 castings (which are widely regarded as junk). You are on the right track though, going with the aftermarket heads.