For anyone who grew up in the 70s and read Road and Track magazine you probably knew about the Rokstock. I like to think that this is the 1970s version of the Celica Supra. A reasonable cost 2 door hatchback with 6-cylinder that was easy to upgrade for more performance.
Richard O. Kiser formed a tuner company Rokstock in Tigard Oregon that sold performance parts for the Mercury Capri II. He sold everything from cosmetic parts such as front spoiler, rear whale tail, suspension parts from mono-leaf rear springs and Bilstein shocks, engine upgrade kits, up to converting your Capri into a full RSR Turbo.
He used an Ak Miller draw-through turbo to significantly increase the hp over that of the stock engine. The Ak Miller system used an AiResearch turbo running at 7psi of boost to deliver 175-180 hp. The base engine was a stock 2.8L V6. 9psi boost was also available.
The typical Rokstock suspension lowered the car 2 inches and one of the wheels sold were Cromodora 'Daytona' magnesium wheels in 13 x 6 1/2". These wheels weighed about 9.5 pounds!
13 x 6" version of the Cromodora 'Daytona' magnesium wheel
You could purchase any of the above parts or if you had Rokstock convert your Capri you were given a Rokstock serial number. Apparently only about 35 RSRs were ever built.
It sounds like he ran into financial problems and withdrew from the automotive scene which has increased the mystique of the car.
It was quite well sorted. Road & Track magazine wrote an article on the car so there IS some information about the cars.
What sounds like a partial conversion car surfaced in Calgary Alberta, and passed through several hands. I don't know if there are any other of these cars still in existence.
There is a Capri list which is quite quiet compared to the Celica Supra forum. I think there are a few others here who are members of the Capri list as well.
If anyone has information on other Rokstocks, I would love to hear about them.