Alu OD 833

72bluNblu said
I dunno about that. The 308 bearings came about for a reason, they went to the larger bearing to help make up for the 3-4 gear reversal changing how the power was routed in overdrive (3rd gear on the cluster).

You can buy a 4.8" diameter bearing retainer for the 308 bearing cases (or turn the 5.125" retainer down to 4.8"), and then you can have the 4.3" bellhousing machined out to match the 4.8" retainer. They sell the 4.8" retainers with the bolt pattern for the 308 bearings now, makes putting one behind a big block easier. More info on that on the bottom of this page, they turned it down but I've just bought the 4.8" bearing retainer with the larger bolt pattern since then

Mopar Big-Block A-Body 4-Speed Conversion

So you want to buy a 4.8 retainer, bore the bellhousing to match the 4.8 retainer, and hope that all the machining is spot on? No thanks. I've done this too many times to worry about the 307 bearings. By the time I tighten everything up and have the stronger cast iron case with 90 wt gear oil, I'm good. I haven't worn one out yet, and I've been running one since the late 70's. I can simply slip my O/D in place of the 4 speed, hook up the shifter, and am good to go with easy stock parts that I can put back to stock whenever I want.