Here's a post with part numbers/source Clicky
, the PO of our coach got the one for ours at the same place.
I'll be replacing it with an Aero AT5050 soon for a bit better breathing.
The one in the top link is a drop in, the 5050 would take some fabricating.
The above post is just my experience/opinion which is worth exactly what you paid for it.
'05 Lance 845/'06 F-250 or '99 Alpine 36SDS Usually towing an '01 Wrangler locked on 35"s or moderate '98 Cherokee on 33"s (rear locker only)