Looking at a 1990 Thomas Saf T liner RE with 137000 kms\85000 miles. Has what is listed as a Cummins 8.2, still new at this Skoolie game, did Cummins make an 8.2? Any reasons to steer away from this setup.
Get the specs on the trans, rear gear ratio, mileage, tire condition then look for rust or leaks. Then...you'll have a start on qualifying this beastie.