I have that pic of the John Thropp car in my files. Love the tow bar.
Towed my GTO to the track, in '73, with a 472 powered Caddy. Plenty of torque. No sweat. Hey, I had to start somewhere. For '74, I moved all the way up to a homemade pipe trailer, which had mobile home axles & no brakes. But hey, I was winning races & having loads of fun !
That reminds me of this 3rd pic, which appears to be a GP pulling a trailer with a Bird on it. Have seen a few pics of Pontiacs, especially wagons, pulling other Pontiacs around.
By the way, that GTO in the top pic is a '67. I've seen very few of those on the track. I suppose the GTO racers just didn't wanna give up their Tri-Power & 4-speed. I think the 400 engine, TH400 trans, & Q-jet would have been a lot more competitive. Dial your own, breakout racing, is just tuff with a stick.