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.
A lot of guys do use the stock bracket so mount the lower side of the fans. Trouble with this is it leaves an ugly amount of gap (and bare radiator showing) at the top between the bottom of the top hold down plate and the top of the fan. The bracket I made holds the fan high in the space...