I have a 17 iron. I'm looking at a new fender in vivid black pn# 58900101DH. I think it's stock off of the 48. Will this bolt right on without mods? The local dealership has no clue about fitment.

 

I just ordered a rear fender off of a 14 xl1200T. I have a 12 xl1200c and wondered the same thing. After days of internet searches, I ended up taking screen shots of Iron, 48, Low’s and Nighsters. After arranging side by side by side, I was able to determine that all the mounting points matched. The only major difference between any of them was the 1200T fender. It’s fuller/longer at the tail end than a Custom, but all mounting holes are in the same location. So if you look on eBay, it’s best to keep the years in the same parameter, as if you were buying something from a parts retailer. (Ie; fits Sportster 07- present)
Hope this helps.