Other than the standard route of following NADA and Kelly BB, watch the advertisements and check Ebay out. On these older volvos that weren't maintained, you could be looking at some higher maintenance costs. Granted, if you do the work it's fairly reasonable, but your time should be worth something.

Always a good idea to have an independant Volvo tech spend an hour combing through the mechanics of the car. Usually under a $100 and well worth it in negotiations.

51K is very low for an 89 740T, confirm with mx records, state emission test records, carfax records and anything else you can find. I once bought a 90 240 with super low mileage from a reputable dealer in Orange county, ( I am trying to bite my tongue on this one) it turns out they bought it from a reseller who put to cars together and used the paper work from the car with lower mileage. Buy the time I figured it out I was home in ALaska with more money in roadside repairs than the car originally cost. Clues to inaccurate mileage could be, sloppy doors, noisy blower motor, worn seats, noisy and loose suspension bushings, sloppy steering, worn interior. Also, go the the B-boards forurm for FAQ's on the 700/900 series and should find a section on what to look for in a used 740.

Remember, the 260 has an interferance engine, and lack of attention to required period maintenance could lead to premature engine failure. Take care of it and you'll appreciate the power it offers.