96 rear sprocket replacement issue

[screw it]

I bought my bike used with a 39 tooth rear sprocket with numbers c45 under an image of a rising sun and part number jtr828-39. I was sure this was the incorrect size so when time for replacement came ordered what i thought was a stock sprocket from onlinecyclepart.com. they sent me a 48t sprocket part number 48p-25448-21. although this sprocket it much larger its more of what i was expecting but on top of the huge jump in size the center on the new sprocket is also must larger. my question is do the list the wrong part for my 96 seca or it there a chance someone has swaped the clutch up as well to fit the smaller sprocket? pls help!