It all depends on the definition of good. More details are needed before an accurate appraisal can be given. If I was going to spend that kind of money on an engine, I'd want to make sure it had good compression, a leak down test was performed, the mileage of the engine was known, and if it had any mysterious loss of oil or coolant while it was running. The seller should be more than happy to provide these things to you and if asking for them makes him uneasy, I'd walk away. More info is definitely needed.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo