I'm rebuilding an older model 22R. Problem is, it wasn't in a vehicle and I'm unsure which version it is. The "early" model came in two flavors. One was produced 81 - 2/82. Another was produced 3/82-84. The "new", single cam chain version appeared around 85. I believe this is one of the early versions since the head has rectangular intake and round exhaust ports, and it has a dual cam chain. I read about a swirl-port intake in several posts, but I haven't a clue what that would look like. Does anyone know what changes were made 2/82 to 3/82 and how I can tell the difference? I know they require different intake and exhaust gaskets, but I'm not sure how they differ. Any ideas on determining which gasket set to order? Thanks, Barry