From the Monoposto rules-
Vintage Formula Vee is a class for single seat racing cars based on
components from the standard Volkswagen 1200 series Type l, U.S.
model sedan, as originally manufactured and imported by VW from
1961 to 1965. Since it is a restricted class, all allowable modifications
are stated herein. Any Formula Vee manufactured prior to January 1,
1976, is eligible for Monoposto Racing Formula Vee provided it
complies with the following rules as used in 1969:
A. No component of the engine, power train, front suspension, or
brakes shall be altered, modified or changed, nor be of other
than VW manufacture, unless specifically authorized herein.
B. The bodywork is the original bodywork, or is substantially
identical to the bodywork installed when the car was originally
manufactured.
C. The car must originally have been manufactured two springs
and two shocks as the supporting devices for the rear
suspension.
D. There must be a VW fan shroud, working fan and working
charging system as described in paragraphs below.
E. Minimum weight, without fuel or driver is 825 pounds,
wheelbase is minimum 81.5"; maximum 83.5" and track is front
51.4"; rear 50.7" [standard VW sedan]. A small tolerance is
allowed for cars using the permitted 4.5 inch rims. Overall
length is minimum 123" and maximum 127" with the body depth
at firewall: minimum 25"and maximum 34".
Even if it was built after 1976, if it is set up in a pre-1976 configuration with two shocks, working fan and charging system with treaded tires it should be Monoposto legal.