Depending on what was changed, just the block, or the head, or nearly everything, it can be a chore nailing down exactly what engine parts are Renix and what is not. The heads have a stamping number on them. Old_man listed some real good head and block clues for sure. The exhaust manifold is a bit different the intake manifold and throttle body areas have differences, but some people swap just a block or a head, etc....
There should be some online sites that show the location and numbers for castings. I saw one for the heads I posted here recently. The valve cover and VC Vent line was also noticeably different.