Auto Atlanta sells rotisserie plans for $16.50. If you dig in online, you'll find them posted.
There is another site with detailed plans...don't recall exactly...a google search will find it easily.
Edit: Found:
https://blueskymotorsports.com/index.php?op...18&Itemid=6I built mine last year for about $600...including the heavy duty rotating heads I bought from Jegs (80042-5) and the heavy duty polyurethane casters from Tractor Supply (SKU 353001299). The center piece is a galvanized 10 foot pipe from Lowes.
I did offset weld the rotating heads...the body shell was still a little top heavy, but, I could manage rotation by myself.
I also built mine a little taller to provide plenty of clearance for the fender flares...the whole unit still fit into a standard height garage.
I'm probably at a point where I'm ready to sell mine...shipping from Louisiana would, unfortunately, be cost prohibitive.
If interested, I could take a few measurements of my rotisserie build.