As to the question on strengthened subframe mounting points, the unibody is the same as the 325is.

As for the body work, the standard 325 allows for a more effective splitter as the lower valance slants inward as opposed to straight down as with the M Tech. The M Tech "lip" is much shorter (and rounded, and thick and downward slopping) than could be used with the standard 325 to the maximum of the rules. So you could conclude the M Tech is less valuable as a donor and all the fuss made out of it over the years was time wasted. Looks nice though.