Here's some pics of the rotisserie I built for my 68 Acadian (Nova).
I used 2 1/2" square tubing for the main body. I used 3" for the piece attached to the bottle jack. I then used 2" for the cross bars that bolt up to the rotesserie and the car. I used 4" castors that were welded to the bottom. The four on the end are swivel with brakes. The two in the middle are stationary. I used gussets everywhere just to put my mind at ease.
2" tubing. These were both cut to be the same length.
Bottle jacks that I used
Bolted to the car