Chances are very high that the Ohlins will have a 46mm piston, which was pretty much the standard for a long time. This means that lots and lots of different springs will work on lots and lots of different shocks.
Websites like RaceTech's will give you the rate and dimensions for most bikes made since the mid 1980s, so you can work out which bikes have springs with the right rate for you. Its a slow and tedious process, but it can save you lots of money... (I've managed to avoid buying four different shock springs, simply by re-using springs off other bikes: The KDX175 spring went onto the 86 KX, the 86 KX's spring went onto the 88 KX, etc etc).
The mid 1980s Ohlins (I haven't been inside a newer one yet) are miles ahead of the Jap stuff of the same era - they're about equal with mid-1990s KYBs in terms of the technology and how well they're built.
Nothing weird or scary about how they're built either.