I think there's a possibility of a push-rod 496cu engine. Just take the Vortec 8100 out of the trucks, put in different heads, cam, lighter rotational assembly, and call it done. Ditching push-rods seems to be a foolhardy move, since they have no problem supporting higher lifts and durations than have been used up to now, and GM is very well versed at building push-rod V8s.