I recently bought a built 700R4 from a 90 GTA to bolt up to my mild 355 and drop in an 89 RS. Not too much on this car is stock anymore...definitely not the wiring. So, this 700 was a VSS style speedo output. I've got a bunch of cable drive speedos. So, I take the driven gear and cover off of a cable drive 700 and try to swap it with the VSS gear and cover. I thought it would work no doubt. NO! The teeth on my VSS and cable drive gears are pretty different. Teeth on the VSS are wide and cable drive gears are thin. Do I need to swap the mating gear (the one on the output shaft) from the cable drive unit into the new trans as well? Would I be better off to get an aftermarket speedo and hook it up to the VSS output? Help.

I just found out that:
"Not true...up to '89 was different 2000 pulse

'90-'92 4000 pulse, like the one in the picture."

So, up to 89 is a different speedo drive unit, I guess. I also read that Firebirds changed their unit in 87 or 88.
My new question is now:
What do I need to do to use one of my cable driven speedometers? Do I need to change the set of little plastic gears OR was there a cable driven car speedo made post-90 that I can bolt in?