The pictures can be wrong a lot of the time I found when searching.

Just go by the part number and you should be good.

for instance, this is the part I bought, but the picture they show is different:
https://www.canadasmotorcycle.ca/fmf...-4-040630.html

 

I think you're correct, if you look at the proportion of the outlet diameter on that link you just posted it looks like the stock 1 3/8 opening. The picture in the first post from the OP looks like the outlet has a thicker lip, indicating a smaller outlet. I'll quit debating and just go with the appropriate part number.