l have a 1990 Lincoln Towncar with a bad air suspension. The airbags leak, and the compressor finally gave out as well. Strutmasters.com has a coil spring and shocks conversion kit for $269. Is this a good price? Are these parts custom made, or canl buy some universal parts separately for cheaper?

As the Lincoln Continental was based on the same chassis as the Taurus/Sable.Check with your local parts store for springs, struts, etc. for a 1990 Ford Taurus or Mercury Sable.

The parts listed on the website do not appear custom made, you would probably be paying a higher price then collecting the parts individually.