The 740/760 Turbo used non-watercooled turbos up through the '86MY, so I would stay away from those unless the turbo has been replaced with a watercooled one. The '84 760 Turbo has the strongest engine with a forged crank and rods. The '85-'88/'89 is the weakest, with small connecting rods and a cast crank. By late '89 the B230FT had improved crank bearings and larger connecting rods, which makes this one desirable. From '90-'95, the B230FT used a smaller turbo (Garrett T25 or Mitsubishi td04-??) than in previous years, and the exhaust manifold was improved. These cars build boost at much lower rpm and accelerate quicker, but the top end power is not as good as with the older Garrett T3 turbos.
The last year for manual transmission in the 740 Turbo was '91, and the last year of production was '92.
Check the intercooler hoses to make sure they aren't soggy and soaked through with oil. Make sure the turbo builds boost and doesn't smoke.