Yep, when the cylinder head designer moves the rails the gasket mfg gets the blame!

I've probably said this a million times but "not everything works with everything". It isn't like there is an official Mopar aftermarket certification board that hands out stamps of approvals for Mopar parts. People just make stuff and sell it and maybe it fits and maybe it doesn't.

I'm not sure why a company like Edelbrock would change something fairly standard like the valve cover rail dimensions but they did. Or at least they did on the early Victor heads that I owned.

My personal way to deal with this stuff is to keep a large collection of gaskets on hand. Any time I'm working on new parts I check them against a stack of different gaskets to figure out which parts will work. I do not know any other way to figure it out. People don't put instructions in the box that say "we changed the dimensions on our part and your existing gaskets will not fit".