One other measurement please:

If you attach the W115 brake pedal arm to the W123 assembly, and measuring from the inside of the actual "pedal" part (where the rubber pad or covering goes) of the brake and clutch, what do you get? Right now, there's 2 1/8" between the 2 (that's inside). The pictures look as if it's less than that. I am guessing if the pedal arms could be spliced and the lower portion bent so that there would be the OEM distance of 2 1/8", that would sold the issue. The pushrod exiting at the point of the firewall will not be more than 4" no matter what ... actually, it's around 3" with the 5:1 ratio.

There's a bunch of calculators on the net for manual brake conversions and it looks as if this could be an ideal scenario with that pedal arm. I need to get one now and stop the presses on the aluminum custom deal.