I heard the 64-67 chevelle convertable frame is a like year el camino frame shortened at the rear bumper "c"rails by 3'..... is this true????
This is not an exact answer to your question, as it is all about wheel base, but the closest I could find on the subject. These are exerpts from Wikipedia:
Two station wagons built off the A-body used stretched wheelbases and raised rear roof sections with skylights. Those included the 1964-1972 Oldsmobile Vista Cruiser and the 1964-1969 Buick Sport Wagon.
All A-body cars except the long-wheelbase wagons rode on 115-inch (2,900 mm) wheelbases from 1964 to 1967, with the wagons using a 120-inch (3,000 mm) wheelbase. For the 1968-1972 models, wheelbases were 112 inches (2,800 mm) for two-doors, 116 for four-doors, El Caminos and station wagons; and 121 for the stretched-wheelbase wagons.
Also using a variation of the A-body chassis and suspension were the 1969-1972 Pontiac Grand Prix and 1970-1972 Chevrolet Monte Carlo - both of which were marketed as intermediate-sized personal luxury cars and coded as G-body cars with the GP riding on a 118-wheelbase and the Monte on 116 inches (2,900 mm). When the A- and G-body cars were restyled for 1973, that G-body design was renamed the A-special body.
The Chevelle was intended to compete with the Ford Fairlane, and to return to the Chevrolet lineup a model similar in size and concept to the popular 1955-57 models. Enthusiasts were quick to notice that the Chevelle’s 115-inch (2,900 mm) wheelbase was the same as that of the 1955-57 Chevy.