Regular 289 cast iron exhaust headers vs HiPo model

I own a 1965 Mustang convertible with a 289 engine, 4 speed toploader and the regular cast iron exhaust manifolds and a dual exhaust system. I am installing a 302 engine that has the HiPo cast iron exhaust manifolds. Will these manifolds bolt up to the existing dual exhaust system or will I have to modify it.
Regards
PopyRed Ragtop