Bro, if ur talking about tep R n b16a head then u r right...they are from the same cast but different internals...however, B18C GSR head is different...simply use mr google to find out more...
here is one ...http://hondaswap.com/general-tech-maintenance/b18c-b16-head-differences-56721/
here is one ...http://hondaswap.com/general-tech-maintenance/b18c-b16-head-differences-56721/