Okay, I was mixing hardware and software designations.  My Freightliner has 24.5" hub centered wheels, my Trinity trailer has 22.5" hub centered wheels and my Merritt trailer has 24.5" lug centered wheels.  While there are a lot of options for tires, I still need to match tires to wheels and wheels to hubs.

I was thinking that the software and hardware had a compatibility difference between 32 and 64 bit; it's good to know that is not the case.  But going with a 64 bit OS seems a little like going with super single  tires.  Sure there are some advantages, but you don't limp in with a flat as you do with a flat on one of the duals - and replacement super single tires and wheels are not going to be available everywhere.  If I go with a 64 bit OS, what issues will arise regarding current software and drivers?

Thanks all for the help.