Not an expert here but, Id want to check that everything turns freely, in all gears, so first turn the input shaft in neutral, then output shaft, then go to the side and work the levers into each gear and spin it.. after that damage to the case and missing parts, chunks of metal missing around the tail shaft seal etc. same for the bearing retainer, make sure the retainer is there, and not missing broken...after that you wont know till its in the car, (from experience, mine wouldn't shift into third easily, turned out to be broken dogs on the synchro) you may want to plan on going into it before installing in the car, either way they are fairly quick to get back out of the car if there is an issue...
