One of the Pontiac 1:1 restorers has a '65 sportsman car that is quite a combination of parts and pieces...don't recall frame origina, but it uses '56 Ford (maybe Lincoln?) uppers and the Park Lane Mercury knuckle, with the big Buick drum brakes.

Sits too high to be a good speedway car, but on a short/intermediate track it might have some juice.

In scale, I'd use a scrap cage and rear-steer pickle fork from one of the throwaway Cup cars, with the '65 Chevelle Late model chassis, could probably fake up a nice Pontiac engine out of parts boxes.