I've analysed the various cars eligible for the Vintage Sports class and have determined that there are four different basic chassis designs shared amongst them. For want of better names, I've classified them as Type A, B, C and D (this last type is universally known as a "Sebring" chassis). Listed below are the chassis types and cars which use them, followed by pictures of the bottom and top views of the chassis gleaned from the car reviews.
Type A:
Revell-Monogram Cobra Daytona, Corvette Grand Sport and Jaguar E-Type:
Type B:
MRRC Cobra:
Type C:
Revell-Monogram Lola T-70:
Type D (Sebring chassis):
Revell-Monogram Porsche 904, King Cobra, Chaparral 2, Ferrari 275 P and Ferrari 250 GTO/LM
MRRC Ford Mk IV, Chaparral 2F, Porsche 910, Porsche 904, Chaparral 2A and Cooper-Ford:
This should help you decide which model to order.
Gordon