The bike with the sportish rear are indeed European style. The first TR1's in holland had this tail. Yamaha did mess around with types and engines. In holland the TR1 had 980cc In '86 The XV920RJ was imported from the States(!) and had 920cc. The model of the XV920RJ was in Germary called TR1. I thougt those engines were 980cc.
The sportish rear can be mounted to the other bikes but you also need to mount the seat. I all fits on the same subframe.
My first TR1 had this tail. Look at www.imageppo.com and look at the "motor" page to see it!
Eppo.