There are two ways. One is to build a car and join Rocky Mountain Vintage Racing, RMVR, or build a car and join the La Carrera PanAmericana group.
If you build a car for RMVR it will have to meet the General Competition Rules, GCR's for a particular year of competition. My car is built per the 1970 gcr's, sort of! Engine size was limited to 305 cubes, 5 liters. Building a 305 cube Mopar is a challenge. You can either put a 3.58 stroke crank in a 273 or scour the earth to find a 2.96 stroke crank and put it in a 340 block. The 3.58 stroke crank is easier to find but the small bore size may limit flow into the cylinder. I have never built an engine with this combo but I am curious about it.
I don't know what rules a person would have to follow to build a car for the Carrera group. They are a great group of guys that race from the tip of mexico to Nuevo Laredo in Texas and also in Baja California.
The other thing I have been encouraging people to do is go to the hill climb website,
www.ppihc.com, and tell them how exciting it was to see the vintage class on the mountain and you would like to see more.
Jess