What's the most common place on the tranny that leaks besides the spedo angle input.
I'm noticing some trans oil on the heat exchangers and garage floor but can't really tell the location on the case.

I've got mine out on the floor right now, changing seals. There are only five main leak points, as best I can see, and one of those (input shaft seal) won't leak on the HEs. The others - besides the speedometer cable adapter - are the shift selector shaft seal (for sideshifters) and the two output flange seals. Those should all be relatively easy to spot, however, so I'm not certain how those could be missed on inspection.

Is it only dripping on one side of the car, or both?

I'm going to degrease it later today then drive it tomorrow then check when it's hot after a drive.

Clean it down and run after a drive,place piece of cardboard underneath when parked,done this for years always works.
Is it gearbox oil or engine oil ? ...just asking as the smell is very different,Iam thinking output shaft seals,see how you get on.

Trans oil for sure,nothing like the smell of 90# oil!