Actually, the frame shown above is not the one I have in mind. We actually have a thunder ranch, but the frame is NOTHING like that one.
This frame is from Vintage Spyders and I think this is more what you need to start with. This is very similar to the frame we have. The front of ours is significantly different as we have double A-arm w/coil over with rack and pinion. This frame in the pic is VW front end. Hope it gives you some great ideas.
angela