Regarding the car construction and origin, if I can summarise the bulgarian language posts, the most plausible opinion until now seems to be, that this particular vehicle was something of a freestyle exercise, or test bed, made by some of the engineers and techicians, which have worked in our Bulgar-Renault plant, in the early 1970s.
For this conclusion, speaks also the colour of the registration plate, which indicates that this vehicle is government owned. If that is the case, the photos /and the movie/ in which are visible the set of wheels from Renault 17, may have been made later in the life of the car, so in mid to late 1970s, possibly the wheels were then added to the car.
In the short period in the movie around 4.30 min, exacly before the entrance of the homemade car, most of the other visible cars are very famous bulgarian rallye cars from the beginning of 1970s.
So I suppose, the homemade car was used for something of a demonstration run, before the actual start of one of this big bulgarian rallyes in the period.
Dropping a link to: http://www.allcarindex.com/search/country/Bulgaria/?f=1&i=mod where some other homemade Bulgarian cars are listed. But sadly not this one.
Thanks for the link, there is some photos, which I havent seen until here.
On the fourth photo is seen a vehicle, which represents one of the few bulgarian attempts of making a pure sports car, during the socialist period.
in this case, the two seater mid-engined Sofia Type B. /The exists a predecessor- Type A, which was was some kind of d Buggy, and Type C was also an open topped preasure car/.
In all, there have been built around 7 or 8 full complete cars Sofia B cars, in the period from 1984 to 1992, or something.
At least, this is my observation from back than. The Sofia B main constructor and boss of the small government-funded firm, which build those cars, was the late eng. Velizar Andreev.
During my study in one technical gimnasium in the capital Sofia in the mid-1980s, I was able to spend two summer holidays, working different things on number 2 to number 4 built, Sofia B-s.
Here on the 4-th photo you see number 1 or number 2 built Sofia B, because only the two firstly built cars, have this allmost upright A-pillar on the front window. All the next cars from this small batch of Sofia B-s, were with more slim looking and normally cambered A-pillars.
Interesting footnote on this photo, which is taken on the street in front of the house of the constructor eng. Andreev, are the two Volga-s, GAZ-24.
These were the two regular personal cars of the engineer, and on the white one, he have forcefully cut the metal roof of the car in 1985, so he drive in style, in the hot summer of this unforgetable year.
Interestigly, the structure of this GAZ was so strong, even for a car without chassis, that it didnt collapse immidiately, and was still drivable after couple of years later.