I thought about doing a similar job on my 300SD after I raided the drivetrain out of it, although I was leaning towards a domestic V8 and auto to just get it resold. In the end, it simply looked like more work than I wanted to put into my non-project vehicle, and so I parted it out and scrapped the carcass. I probably could have gotten $1500-$1800 with a GM or Ford small block, but in the end I would have had so many hours to get it right that it just wouldn't have been profitable.