These JK chassis were just called a Cheetah. no II or any other number. These were available in two different 4" wheelbases. I have one short one, I have a number of Cheetah chassis parts. What I don't have is their aluminum pans, I ran one in a NASCAR race on a king track until the motor blew. A friend of mine set one up for GTP & it was a sweet handling car when I drove it.
I liked enduro races. Me & a friend organized a 4 hr at night with car lights on the local 185' Engleman. We used a flexi with a S16D motor & a JK GT-1 body with the stepped rear spoiler. The track owner didn't know much about endurance races & didn't have another one. Back in 1968 the local raceway in Maine had an 8 hr race at night wit h car lights. It started at 9:00 PM & finished about 5:30 AM. .I took my 14 yr, brother with me to marshal. About 1:00 AM he fell asleep in a chair, so I dumped him on the floor to wake up.