The centre shaft will work fine with the plastic MSX bearing holders and top brace. you just need to turn them round, thats all (they hold the bearings captive, rather than relying on the c-clip and end stop on the MSX layshaft).
The alloy braces are simply to allow you to raise the centre shafts to fit bigger spurs on the car, they aren't specifically needed to run the MRE centre unit.
HiH
Ed