As I said earlier, the wear is caused by incompatible materials. Nothing to do about sizing. If the shaft slides down past the bush, the size is ok. You would know that straight away by inserting the shaft into the bush. There are many grades of bronze [ eg, alum bronze, phosphur bronze ]. The bronze used is a grade that will be compatible with the hardened factory shaft. The aftermarket shaft is made from a Moly steel 4XXX, which is tough, but not hardened, & it will accept some twisting from a high pressure oil pump....but not break. The factory piece is brittle & will snap like a drill bit if overloaded. I am surprised the sellers of these drives do not include, or at least offer, an alum bush with the drive.
The drive in post #28 has less than 2000 miles on it. Imagine what it would look like after 20,000 miles!