DanB

The heads on a 525 are made by Edelbrock, and unless they did something different just for a 525 which I seriously doubt, any BB header should fit. They prob raised the ext ports like the Merlin heads are, but the port location and header bolt pattern are the same. But...stranger things have happened. Might call Edelbrock to confirm. The cmi's prob have 32" runners vs the short runners the E tops have. I dont think they make the 2 piece split tubes any more.

T/Motorsports

When I talked with CMI,The 525 headers will also fit the 500 HP heads also,The bottom 4 holes are the only difference put the 500 HP header gasket up to the header and drill 4 new bottom holes in the 525 style header, Then they match perfectly to the 500 HP heads, Per CMI.