Over the years I ran my 40 Chevrolet Coupe in Vintage Gas coupe, Vintage Altered and Fuel coupe, and Vintage Gas Comp coupe meeting the rules each time. Listed below are the configuration. It had a GMC for power. I hope this helps.
Gas Coupe..All stock body including running boards, head lights and fender mounter parking lights, bumpers and rearlicense plate and mount.
Altered and Fuel Coupe..Running boards removed, head and parking lights removed. grille covered, bumpers
removed, license removed. (not practicable to remove front or rear fenders on this style car even tho legal)
Comp Coupe... All above plus a fiberglass bumper/nose extending the front by 18". (easier than a belly pan or a greater than 25% engine set back)
I set and held records at Bonneville in each of the classes listed above. The car was a true vintage gas coupe and still is; however with the changes I was able to run in the above vintage classes legally.