I had the same issue finding the appropriate o-rings. Turns out after 40+ years they tend to shrink a bit. I opted going for the slightly larger hoping they would squeeze down on the shaft a bit more. The one I rebuilt I had to take a lot of metal off because the snap ring scored the shaft a bit. If I can get it to seal with a previously scorn shaft, I am confident yours will work out fine. After over a month after rebuilding, still no signs of a leak.