OK, here are some times (10 laps or so of fuel)
SHELBY GT-350R CASC 1.33.5 (quicker now)
SHELBY COBRA 289 ROADSTER 1.34.2
SHELBY GT-350R SCCA 1.34.3
CHEVROLET CORVETTE C2 L72 COUPE 1.34.6
E-TYPE LIGHTWEIGHT 1.35.1
FERRARI 275 GTB/C 1.35.6
CHEVROLET CORVETTE C2 Z06 1.35.6
FALCON WESLAKE 1.36.1
CHEVROLET CORVETTE C2 L76 ROADSTER 1.36.8
ALFA ROMEO GTA VOLUMETRICO 1.36.9
FERRARI 250 GT SWB COMPETIZIONE 1.37.3
The GTA and the 350 had very few laps and may be faster now. The 65 z06 vette is too quick for it's group, but the 62 cars are about right. Trouble is, they are pants to drive compared to the 65 car - understeer everywhere
[updated with e-type, falcon & 275]