extremely different - your saving alot of weight up front first of all (if aftermarkets are ALUMINUM) and your never gonna get the same flow out of those cast E7's as you will out of a set of Eddy RPM's or TF Twisted Wedges, or AFR's - do it right ONCE - go w/ aftermarket heads - and get a cam while your in there, cams are cheap - and you don't wanna hve to tear your motor apart more than once