I am nearly 60 and have beem messing with engines for the better part of 50 of those years. I have done numerous car engine swaps, a couple of motorcycle swaps, and many, many rebuilds. I have worked on everything from .049 model airplane engines to 40K hp Fiat marine engines in the Persian Gulf. Their cylinder liners are 1.1 meter in dia. and nearly 4 meters long. We installed 4 on them during the Iran Iraq war in 1984 in a super tanker off Bander Abas, Iran while Iraqi pounded the crap out of the Hormuz terminal near by. Not that this makes me a hero, only that it means I have done my share of weird mechanical projects in 20 years of living as a free lancer over seas.
If one were not going to go where Mr. badbenz.com went,(and, I must say, it looks like he did a masterfull job) I can't see that a new, warmed over sbc 350 and even a GM 700 overdrive trans. would cost more than $4K installed. Buying a salvaged MB 450 engine without going through it completely is basically buying someone elses problems. Going through a 450 I doubt would give one much change out of $4K. Then, when the 450 is complete, you are tied to MB's exorbitantly priced spares and service for the next 150k miles.
Don't get me wrong, MB makes some stunning cars and engines. I have been through the MB museum in Stutgart twice and the bill of fare there is beyond compare. But, being of Yankee extraction on my father's side, I tend towards the practical more than the purist side of the issue.
If I did not have the highest regard for MB's products I would not be drooling after a silver and black Euro model slc.