I to have looked far and wide for info on a MB conversion and found nothing. I understand that the 350 SB Chevy is just a bit too wide to go into the sl/slc. Apparently, Ford 351 (5.7 l) engines have a bit narrower 'V' and might be a candidate. I don't know about the Chrysler 5.2 (318 ci.). If they fit these would seem like great engines. It wouldn't take much in either time or money to get 300+hp out of one of these dudes. As mentioned, the width of the tranny might prove a headache unless one could adapt the MB tranny.
You realize that the main problem with the above is that you would be forever banned from the MB board. Of course with one of these engines you might not need to refer to this board as often either.