I'm thinking of buying a 96 STS or Eldorado. Both cars need a head gasket job, or an engine swap. Several shops say that I could have the same problem in 10k miles, so they won't warranty beyond that, or 90 days for one shop. Can i install an engine from an 84-87 Seville or Eldorado? I haven't heard of any problems that aren't worth repairing from these model years.