Edelbrock Valve Covers, interchangeable from stock to aftermarket heads?

Yes they can. Aftermarket heads have the bolt pattern factory Ford heads do.

well i got a 1990 mustang.does taller valve covers do anything really.i was going to take the engine out and put it in my 89.

They look better, but the main reason for taller covers is to allow roller rockers and possibly a stud girdle.

so a regular valve cover seal would work fine.I meen i like the rubber ones but i want to take it off and check it out.

I also have a different size oil pan but not sure on the make or brand or whatever,i know it is a bigger oil pan.would the gasket be the same for that?

yes all your gasket will be the same part # as stock