This isn't one of those "how many rotors does it have?" threads. Specifically what engine parts are different between the two engines and what are interchangeable? Obviously the eccentric shafts are different, but I assume the rotors and rotor housings are similar.

I know it's probably been covered before; I tried searching and just found a bunch of BS threads with no information, got frustrated and came here.

 

the 20B uses S5 T2 rotors, and all the seals on the rotors are the same as well. oil pump and front stack is like the FD.

the thin irons are similar to the 13B cosmo irons, although there are a couple of differences, for instance the 20B has a few bigger tension bolts, so there are some holes that are bigger. the front iron has tension bolts going through it the other direction, as the 20B has bolts that go from both sides.

the stationary gears in the front and rear are FD style.

the Eshaft, center iron, center bearing are all obviously unique. as is the oil pan, which is NLA new. some of the tension bolts are different, and there are more of them.

the rotor housings are also unique to the Cosmo, it has a different exhaust port design. the FD housings go right in, and at this point are the only ones available new anyways.

the water pump is completely different, although it uses the FD water temp sensor (actually the FD uses the Cosmo sensor). the CAS is different than the FC, but works the same, and the FC part drops right in.

the primary injectors (550cc) are unique, as is the fuel rail. the secondary injectors are S5 T2 units, so are easy to upgrade/replace.

TPS is unique to the Cosmo, although its electrically the same as the S5/FD

not much of this is really news.. its all in the parts catalog