Using the early version of the M104 engine from '90-'92 wouldn't be difficult because it uses the same CIS fuel injection system that your car currently uses. It is a 3.0 liter DOHC engine, and it puts out a lot more HP than your current M103.

The '93-'99 3.2 liter M104 engine would be hopelessly expensive because it uses the all-electronic fuel injection / management system.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".