I think I understand that the ratio of the speedometer drive gears at the rear of the transmission varies with the ratio of the particular final drive (ring & pinion gears, or crown gear set) installed in the car's rear axle.
In other words, it varies from car to car and does depend on -- or is matched to -- your rear end ratio. It can be counted in a disassembled transmission, and surely must appear somewhere in some technical tome such as the TDM. I haven't come across it, but if that reference can be identified by someone here, then the final drive ratio -- as inscribed on the exterior of your differential housing -- would provide the key needed to solve this question with no disassembly required.
Failing that, I'm pretty sure I know where there's a manual transmission sitting open and eviscerated in North America which could be useful. Either way, though, the inscribed ratio is a necessary piece, as the one I have in mind is near to yours in age and model but not necessarily a match, and for that matter, none of us yet know which ratio your car has in it's rear axle. [Mine doesn't even match the information on it's data card, as the axle was swapped for one with a preferred ratio, demonstrating that it's best to crawl under and check for sure.]
You'll be looking along the bottom left edge of the differential housing, on a flat, smooth area of the vertical surface ~ 13mm high and running along pretty much the length of the housing if I remember correctly. There are two groups of numbers lightly incised -- manually inscribed -- on this surface. The set of 3 digits toward the rear, separated by a comma, give you your ratio. Odds are it's "4,08". Take a good light and a sturdy cloth, and maybe a little solvent with you, as the figures are not deeply stamped such as you may be used to on our domestic iron; it's more like fine pen scratches ... very graceful.
