I have the 15x10 aluminum rims. I also run aluminum drums. 290x50x15's. No frame notch but the fender lips are rolled. I can't imagine fitting any more tire in there. Drop springs also. I do run drag bags to limit travel.
When I did my overlay I sent my entire cluster to Casper's and they recalibrated it. There are gears inside they can change from my understanding to convert it correctly to the new indicated speed.
I would imagine that the reverse could easily be done too.
I make a mounting bracket for the Intrepid fans. It holds the fans up in the radiator so the top is held in place by the factory tabs on the radiator top plate. I sell them direct on eBay and thru Kirbans and GBody.
I primarily sell them on Ebay now. Just search for Translator Bracket. I am seller OceanLovers*Beach. Everytime I revive the thread on here I have to go thru the same hoops and essentially get permission to since I'm not a vendor.