The gear cuff helps keep the shaft from spreading apart under load which breaks the outer case, break gears or totally detroys your trans. I did machine the inside of the awd case, I just added a chunk of aluminum and welded some pieces to the outside of it. The gear set in the pics above are for my Altima not for the Bluebird but most of the parts are the same since the both have 50A gearboxes the only different is that one fwd and the other awd. The trans parts in the pics were made by PAR engineering, almost all those parts are off the shelf, only the gear cuff , ring gear+main shaft and input shaft were custom made..