Neck shape on RR Burny's do vary a lot because they were made in 3 different factories from 1983 to 1998;
1983-1985 Kasuga
1985-1986 Matsumoku
1987-1998 Dyna
The Kasuga customs do have the thinnest neck on average, the Dynas (especially the ones around 1989-1990) have the thickest neck.
Regarding Greco's; these are MC collection, so a little thinner neck than the Super Real era.
There was a RR55 and a RR65, the difference only being the pickups; resp, screaming and Dry pups. Dry 1982 pickups are reported to sound very similar to Dry Zs.