Do a search of the forum mate, theirs loads of threads on here about them. Ive just made one myself for my rally car. makes life a hell of alot easier. its only a simple one but i can send you photo's, drawings of that if you want.
Silly query perhaps but is it possible to spit a vehicle without disassembly, I know the fluids need sorting , got a transit that needs a good clean and paint underneath but did not fancy crawling under it to do it?
If you want to get detailed drawings of a brilliant rotissierie, check out the Harwood Performance page on the web. Go to his section on the 1941 Buick restoration and you will find complete plans, photos, build of materials and an update on the tie in between the end roller stands. This will hold a really heavy body / chassis,
My workshop team here in Perth WA, have built one using an old semi trailer axle end, complete with the hand brake roto-chamber, brake drum and hubs. We have used duplex sprocket and chain drive via a speed reducer, and an electric motor with a hand held switch box and umbilical.Hooking air up to the roto-chamber releases the brake and we can get the speed down to 1 rpm, allowing us to weld equipment buckets etc .
Use your imagination and you will be surprised at how creative you can be, without laying out a great cash outlay.
Late model rear hub and stubs work well and using a cable operated disc type hand brake and a drilled steel rotor with a spring loaded safety pin, can also be very effective and safe, to control roll over speed.
Something i knocked up for a Shell only setup, This will take running gear but no engine/gearbox as i think it would be too much weight
No sizes im afaid i designed this to fit a bmw E30 but im sure you can fab your own up, Also i put wheels on myne so i can move it around etc all from 50mm box and a few bits of 60 box where the bearings sit.