@Kyle, from the 2012 competition regulations, there is no mention of homolgation needed or hand-built being disallowed. Just roll hoop configuration, and the safety specs for all cars, belts, fire bottle, transponder, egress. Your car would be Etc. Can't wait to see it.
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All Formula Cars constructed
prior to January 1, 1998, shall be grandfathered in their original roll
bar/cage/chassis design so long as they are competing as an
ICSCC licensed entry with an appropriate ICSCC logbook.
Grandfather provisions notwithstanding, the top of the roll bar main
hoop shall extend two (2) inches above the driver’s helmet, seated
normally and restrained by seat belt/shoulder harness. Additionally, a straight line
cont. drawn from the top of the main hoop to the top of the front hoop,
shall pass over the top of the driver’s helmet. New cars
constructed after January 1, 1998, shall have front hoop/rear
hoop conforming to Section 1105.
. . .
Formula Libre will consist of all open wheeled vehicles not
aforementioned (i.e., Formula 5000, Formula Continental,
Formula Super Vee, Formula B, etc.).