The 8.8" conversion has been done on a friends car, by welding new brackets to the beam.

He uses two short Cosworth drive shafts, and modified 8.8 yokes. So far split one drive shaft and three joints.
I'm gonna try doing more of these conversions. For my own setup I have custom made yokes, which lets me use stock Cosworth shafts(both 2wd and 4wd).
I'm also working on a jig, which helps me place the 8.8" in the stock location.