I heard of someone that made up a set of small bolt pattern wheels by cutting out the centers on some stock steel factory wheels and putting them in wider rims. Has anyone here done that? ( I have a MIG wire welder.)
I was wondering how you remove the centers and what 15" rims (7" or 8"
wide) they would fit in. How would you mock them up with a dial indicator to know they were straight?

The "wheel shops" have a lathe with a large "swing" to do this. The can chuck the factory wheel and cut the weld area out which frees the center.

Once you have the centers loose, it is a matter of installing them into new rims at the selected "backspacing". True them with a dial indicator and carefully tack weld in many places before doing the final welding.

I have also seen rims widened by cutting-off ("turning") the inner edge section of the rim and then welding-in a strip of rolled sheetmetal. This takes more welding but it is easer to lay-out for the do-it-yourselfer.
DD