I think we all agree that the B40 should be included in pre65 Dave, providing it has the B40 frame and NOT the later b44 frame that the last B40's came out with. The problem with including the B44 in pre65 is that no one will want to ride the B40 up against the more powerful B44.
Not when we're racing for sheep stations ...
As Firko said, the B44 is a very competitive bike in pre70 with a good rider controlling it. Even more so when it's had the big bore treatment.
I have to admit to having an interest in any attempt to move the B50 back to pre70 but I can't see that happening unless the date was changed to pre72, which, in my opinion, is a much more aligned date than pre75.
But, as the saying goes...If it ain't broken, don't fix it