Never dealt with them personally but Rickson may be out of business and certainly has been a poor service supplier for many years. As far as the entire internet is concerned anyway.
Pretty sure they don’t make aluminum wheels either. But am curious what you consider to be slotted lug holes. In 35 years of being a gear head, mechanic and truck owner I’ve never seen or heard of slotted lug holes.
I did see rickson website compares their wheels to Vision heavy hauler wheels, which are alloy and a “slot” design. The word slot being used to describe the appearance of the wheel and the holes in the rim (not the lug holes).
Maybe that’s what you’re trying to explain.
Regarding your axle, maybe a Ford expert will chime in, but what you’re proposing might be possible. I “think” Ford used Dana Super 60 front axles on all the superduty series from 250 to 550 back in your vintage of truck.
That would be a good start. But I’d think you’d need to replace the entire knuckle, at a minimum to match the mounting points of the larger calipers. Beyond that, idk if the hubs, axle length, dia, number of splines, etc are the same or not. It would be a great upgrade though if it works.
