Just ran across an eBag auction that appears to be advertising (from a reputable source BTW) a single 8.75 pinion seal that works on both the 489 and 741 cases. I was under the impression that they all used different seals. I double-checked the tech archives and sure enough they list different National part numbers. Further research here and here show them as having different dimensions also.

Can anyone shed some light as I am currently in need of a 741 seal and have a 489 one on hand but don't want to open the pig until I'm certain that I have the parts to complete the job correctly.

Thanks in advance!