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Hagerty Employee

ASC left a legacy way beyond chopping tops

The Buick GNX. The Nissan 300ZX convertible. The BMW Z3. The Pontiac Trans Am WS6. The Mitsubishi 3000GT Spyder. The Saab 900 convertible. The Porsche 944 and 968 convertibles. The Chevrolet SSR. These and other German, Japanese, and American enthusiast vehicles were all touched by one huge business empire with the unlikeliest beginnings. That lineage can be traced back to a single man cutting holes in the roofs of cars in a body shop, in a back alley of San Francisco. That’s where ASC began.


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Advanced Driver

Heinz Prechter was also a cordial gentleman, totally honest in every endeavor.  What he lacked in stature he more than made up in graciousness.  The world is a lesser place without him.

New Driver

I thought the WS6 Trans Am was produced by SLP along with the Camaro SS? I believe the article is referencing the hood only, as the cars were actually built in Canada.

Community Manager

Thanks for bringing that to our attention we are revising the article! 


WS6 is an RPO code for brake and suspension package etc. I believe they may have wanted to reference the 1989 GTA 20th Anniversary TransAm that was made by ASC with it's V-6 Turbo very similar but not exact of Buick GNX. I was a Pontiac Master Tech when ASC did the Grand Prix 3.1 Turbo so I was fortunate enough to perform the PDI/Pre Delivery Inspections. That was so awesome in it's time because that car for front wheel drive was a blast! I still own the 20th Anniversary T/A which was the quickest production car in 1989 thanks to the delay of the Corvette ZR1 which didn't make production until 1990 model year.
Pit Crew

@Carnutsatlarge 1989 Turbo Trans Am was done by PAS. PAS also did the GMC Syclone , 92 Sonoma GT, GMC Typhoon.

Let's not forget ASC's work on the Pontiac Grand Prix GTP. I had a 1991 GTP, and at the time, it was the closest thing Pontiac made to the GTO. By today's standards, the 200 horsepower DOHC V6 sounds weak, but it was an amazing ride with big, wide Z-rated Goodyear Eagles!


I hope he found the peace that he did not have here, ASC did a lot of good, and his legacy goes on.

Intermediate Driver

My engineer brother started college at GMI (General Motors Institute). 6 months of class followed by 6 in the factory each semester. He went on to work for ASC. He would come in to family functions with a new pre-production car to drive and report on. One such endeavor was a Fiero with 4 wheel steering - the drive line in those (if memory serves me) was the front wheel drive clip from a Citation mounted as the mid engine of the Fiero. To accomplish this, GM replaced the steering rack with solid mounted tie rods. ASC simply swapped the steering linkage back in for the 4 wheel steering exercise. The issue was getting the front and back steering to respond sharper at slow speeds (for parking etc) but with slower response ratio at speed for stability.  At the end of the tests, they put it back to stock, he bought the car and years later he sold it to me. With the convertible tops, ASC would engineer them, set up their conversion facility next to the manufacturer's main assembly factory. Cars slated for conversion to convertibles would go a certain distance during assembly and when the time was right, travel over to ASC for top mods, then back to the line for final assembly. Typically after this arrangement came up to snuff, ASC would fold their facility into the manufacturer's and move on to the next car company. That's one of the main reasons convertibles come a year or 2 later. They sell the base models while ramping up the new convertible line.

Intermediate Driver

I am really happy to have stumbled on this article today. I’ve been researching my 1972 Lincoln Continental Mark IV that has an ASC sunroof installed. Now as you know all Mark IVs had a vinyl top and you couldn’t just simply cut through that vinyl top and put in the sunroof without finishing that cut edge. And what you cut out of the hole wouldn’t be enough material to wrap around the metal of the sunroof. So when these sunroofs were put in these cars the tops had to be completely redone and that explains why my white convertible top for 1972 is not the factory Calvary Twill vinyl but elk grain vinyl. This is a fact because there simply would not be enough original material to work with once you cut into the roof. And at the same time American sunroof corporation, ASC, Also had another division called Custom Craft, Where they offered aftermarket parts for Cadillacs and Linkins such as half Landau roofs opera lamps and other “ pimp my ride “ accessories. This is a fat I just discovered after further researching this article here. My secondary source is, where they offer an indepth article about Heinz Christian Prechter , the founder of ASC, mentioned above. Mr. Prechter was actually recommended to Lincoln by none other than George Barris the custom car king. So I am really thrilled to finally get all this information full Circle and figure out why my car had copper lamps installed and hood deck mounted turn-signal indicators, which obviously came at the same time the sunroof was installed. You’ll note that Lincoln mercury was adding the sunroof as an option in their printed material but in fact the cars were being sent to another location to have this work done. Also in 1972 this was a $600 plus option, more than enough to cover the cost of also redoing the vinyl tops. These vinyl tops were done seamlessly around the cutout, with the top material rolling over the edges of the sunroof. I’m gonna do a YouTube video about it and updated walk around with my car and I am again so thankful to Hagerty for corroborating this information that I found at