the xflow cork gasket has locating tags but the alloy rocker cover I have and others I have seen have a flat base without these location gaps. Is that going to cause a problem?

Nope, as long as the gasket still seals the cover

Jason

Some alloy covers don't use the cork gasket, because the mating surface is flatter than the old tin cover. These can use conventional gasket material.

Might be worth asking your supplier...

David