JS> Really depends on the individual shops involved. It is impossible to make a broad generalization like that. On a 1987 car I would look for someone with more than the minimum skill set because the car is 20 years old and is likely to require more than minimum maintenance.
Do both use the same quality computer diagnostic equipment etc?
JS> It really depends on the shop. You would have to ask. If you knew nothing about the people you were considering doing business with then your chances of getting someone with up to date equippment would be better at a dealer.
How reliable are the diagnostic computers?
JS> Quite reliable. But even more important is the human mind in front of the screen to interpret the data and implement a correct repair.
Since the dealer looks at a lot more of this brand of car, wont they be
more likely to check the areas they know has caused difficulties on other Towncars?
JS> I don't know much about Ford products, since the last one I drove was a 1972. However for other brands I've found that dealers and independents that specialize in a specific brand are much more likely to know the quirks that go with a specific car. The general purpose repair shop (or gas station) could not possibly hope to keep up with all the quirky ins and outs of all cars.
Which is more likely to try to sell unnecessary parts, dealer or independent?
JS> It really depends on the reputation of the shops in question. It is again literally impossible to generalize about all dealers or all independents. There are good and bad shops in both categories.