In reply to stroker:
Thanks for the clarification.
Formula classes have evolved over many years, but one that has been missed was F Jr.
FA evolved into F5000
FB into FAtlantic with a 1600cc limit (originally) then with mandated Toyota and (later) Mazda engines.
FC was limited to 1300cc engines - later defunct but some cars were updated to FA specs
F2000 - formula ford w/2000cc engines, later renamed as FContinental
AIS - mid-80's IndyCar (CART) chassis' were incorporated into an independent series that specified stock-block, domestic V8's
Super Vee started with air-cooled flat fours until the wasser-coolers were phased-in (mid to late 70's)
There are probably more, but that's all that came to mind right now............