the rs and the hr have the same piston,the same liner ,the same head button, the same timing numbers, pretty much the same ports in the case, the only differance is the water jacket and the induction system/carb. the older purple head is the same as the hr, except it has a normal induction system(wich i think is coming back). i like the rs the best.it easily runs 82 in my rigger. my seaducer with a purple head runs 57.personally, i don't like the hr induction system. some people complain the can't tear down an rs. all you need is an ice pick, some new pin clips, and a couple pieces of brass tubing to reinstall the clips. they aren't hard to work on. o,and plug the water hole to the lower chamber, to heat the motor up.
