The 275DEH is way too much camshaft for an otherwise bone stock 1977 460. Further, the exhaust lobe will provide 0.541" lift at the valve which risks retainer-to-guide interference and could damage the valve train. Since you said that you don't want to execute any valve train mods, your camshaft choices are somewhat limited beyond a stock camshaft. The XE262H is a lot of cam for an otherwise OEM engine as well; low end power will suffer. The 268H is an archaic grind and, frankly, not great for the engine and its appplication.I like the 275DEH it's listed as .515 of lift... I just don't want to do any work to the heads and stuff.. Iam also looking at the 268H it's listed at .494....just looked at the XE 262H it might be the one with .513,,should have no clearance issues I think.