Hi Graham, don't want to spoil the party, but the dominance of BS then on a far superior bike was not too exciting either IMHO
100% agree Renn, I didnt want to rain on Dave's parade to much, and in 1976 Barry had both the full factory RG500 what ever the XR numbers were? Newbold & Williams had bog standard customer bikes as you say painted up to look like Barrys, Williams was pretty incencenced by that & was replaced at the end of the year by Pat, I think Pat though had an equal bike, poss the year befores factory machine?
Rose tinted speccys tend to think that racing was closer in the 70's, it wasnt really much differant, but there were full grids of around 40 riders at all races, which made it a better spectacle for the early laps & those trackside.
I think the answer is 1000cc engines from one maybe two suppliers all sealed & supplied on first day of practice at each GP, put into Moto2 type chasis with 30 riders on the grid, no full factory bikes but factory frames/chasis allowed from whoever supplies the engines, but no complete bikes.
Got to be better than 15 exotic bikes with 6 riders with any chance of a win!