Sorry to dredge this up, but it may be interesting to get some more details of this car.
ascMcLaren used 84-86 Mercury Capris for their conversion platform. There would be no 4 cyl Turbos for 85-86 since Ford never made any Capris with that engine in 85-86.
For 1984, Ford had a 4cylTurbo Capri, insiders called it a "Charcoal Turbo" edition as you could only buy them in the Charcoal exterior color.
I suppose there could have been some crazy prototype from asc for a 1984 Turbo....but...
There are NO records on the 1984 ascMcLarens.....the cars themselves are seriously scarce...no coupes have ever surfaced...and it is pretty well accepted that they were all 5.0 cars.
What color is the car? What makes you think it is a "McLaren" (wheels, parts, etc)? Pictures would help immensely.
When the 1983 Capri was released with the rear bubble, asc introduced a "Sport Appearance Package" which consisted of an air dam, rear wing and Marchal Foglights. Some people had purchased the kit and had the dealer install it...usually these cars are 1983 Capris though....and I have heard people call them "McLarens". Somebody could have installed a "Mclaren" kit on a 83/84 Turbo Capri.
The ascMcLaren discussion group is here if you have anymore details you would like to share and get some more opinions from other people interested in these cars:
http://group.ascmclarencoupe.com
More info than you care to read on Capris can be found here:
http://www.ascmclarencoupe.com/Literature/
(check the Product Fact Books for the engine availabilities each year)
NOW....one last note...some EARLY MUSTANGS were converted to a "widebody" McLaren style...the M81....but they weren't Capris. They only made 10 and they were the Turbo 4 I believe.
-Mike