well sure they do any tire shop can fix you right up... they come in all kind of sizes i just chage a tire the other day was on a 48 wheel i could stand inside the tire go to any tire store
oh yea not only do racing companies like american racing and crager sel these you can have the rims actually made with the backspacing that meets your needs(look in jegs)
but with a mud tire you want a tight bead so you can do things like drop the pressure without rolling off the bead
ie if the tire calls for a 11 inch wide rim go with a 10
or you can go bead locks to keep that tire in place but most states dont like these on the road