I just spent a few hours trying to locate tires for my 83200e. I was looking for the dunlop kt325 which is a direct copy of the discontinued ohstu. Turns out they might have discontinued the dunlops too. Most sites that list them, dont actually have them anymore. I couldnt get any diffinitive answer because it was so late on a friday most places were closed. I'll find out for sure and post it up! I've also heard its becoming increasingly hard to find the kt576 250r/350x front replacement. ther is definately truth to this, as alot of places dont list the fronts, just the kt577a which are the matching rears.
In a few years it will be impossible to find these tires, so if you got any restores planned you better get your tires!!