One is a Greenhead LS (long stroke) with what looks to be a Mac carb. The other is a RS "red head" with a CMB carb. There were a couple different versions of both in the crank induction style. The green head is easy to distinguish, original has a silver case, evo2 has a black case. The red head I'm not sure how to tell among the variations, but I believe there was a RS & a RS07. RS07/second gen has a black case also, but not positive if that is a guaranteed identifier. Both versions of the green head & the RS were also available in valvola style also. Greenhead came out before the Redhead.