Although the last post on this thread that addressed the matter of bell housings and bolt patterns of M116/117 blocks was 15 years ago, it may still serve all of us to correct some of the assertions that have been made over the years.

1) M116 and M117 blocks have been cast in both iron and aluminum.
2) For purposes of discussing transmission attachment, the bell housing bolt pattern on all four variations (iron M116, alum. M116, iron M117, alum. M117) are the same, with one difference: the top two bolts of the aluminum versions are moved laterally 10mm.
3) When the 450SL 5.0 was put into production with an aluminum M117 it was equipped with a 722.006, not a 722.3. That 722.0 transmission was fitted to the aluminum block with an intermediate plate just as it was to the iron block. The intermediate plate was machined with slotted top holes, and provisions for plate-to-block dowels for the aluminum block. It was, in fact, a universal intermediate plate usable with either iron or aluminum blocks.
4) Any bell housing/transmission package that was bolted to a 3.5 M116 will bolt to any other M116/117 engine when equipped with an intermediate plate.
5) An intermediate plate that was originally supplied with an iron block engine can be modified for use with an aluminum block engine.