1972 cut-off for vintage/monoposto FFord ?

[Lotus7]

Just curious if anyone knows definitively how the 1972 date was chosen?

I understand the arguments about one or both ends being inboard, but there are post-1972 with all-outboard. Was there some other technical revelation across the board in 1973 that I've overlooked?

[scorp997]

Most would say it is when CVs replaced rubber donuts, which then allowed inboard brakes, and the mk9 trans.

Side radiators are stated as well, though my car was produced with side radiators in '72. I also have Monoposto papers stating all RP16 Royales are eligible, so there is some wiggle room in the rules

was there a true technological advance, probably not. It comes down to 'cigars' vs. 'wedges'.