N/A LSD's sell in that price range, but you don't see turbo LSD's in that range.
I'm a bit confused about your car though.... These are unibody cars, how can you have an '83 on a 'turbo frame'?
Perhaps what you have is turbo running gear(suspension, brakes) for better handling. If that's the case, all you want/need is the N/A LSD, as you aren't going to have the power to make use of the 951 LSD. You
might be able to get away with an S or S2 LSD though.
Your tranny needs are going to be based on your engines output.
Another thing to consider. Any LSD tranny in the 800-1000 dollar range is going to be high in mileage, and could have worn clutch packs.
So you could just pony up an extra $400 and get a brand new unit,
Click!
Personally, the new unit is the way I'll go when I have the money for an LSD in my 951. Better piece of mind.