This makes me wonder if I can Frankenstein it together. Basically just use the pinion cap from my current starter and swap it onto the one on eBay. I guess it's worth a shot at least. It's not like I'll be spending $100+ on it anyway.Your starter part numbers are unique, but that does not mean it won't fit. However when you look at the end cap O rings they have different part numbers. This likely indicates that the starter casings are different diameters and that could mean it won't fit.
The overall length is probably the same because the screws that hold the starter together are the same length. The idler gear that meshes with your pinion is the same part number, so that's good.
The only way to know for sure is to try it, unless a member here knows the answer.