I like the M104 as used in the '93-'95 124 cars. I've found it reasonably easy to diagnose and work on, not that mine has required all that much attention in 6 years of ownership. Plug changes are trivially easy. There is no cap or rotor. The water pump is a bit involved, but seems to be easier than the 103 engine. This past weekend I changed the fan belt in less time than was required for the topsider to drain the oil.

Just make sure the head gasket and wiring harness have been replaced on any candidate car. Might be worth asking after the ETA as well.

- JimY