I don't think those are really prototype trikes. Alot of people ran aftermarket frames and different engines, especially in some of the pro or open classes. Companies like Nicholson, IIID, and several other makers as well. Some places ran 200cc classes, and pretty much all those machines were custom or handbuilt from one end to the other. There were no factory production 200cc 2 stroke machines. Some of those were sleeved down 250s, and the honda factory "works" trikes, were the european 200cc 2 stroke street bike engines. I think those were called the vmx 200 or something like that.
Nicholson 500x (Project)
Nicholson 185s
Nicholson 110 (That takes an atc70 tank)
Ascott 500 head/350x (Project)
Homebuilt Racer Chromoly Suspension 110 (Ragin Runt)
PK Racing Suspension 70
A+ Inc Suspension 70
AWS Aluminum 90 frame
Hi Performance ATC Suspension frame rd350
Hi Performance ATC Suspension frame 90