Sorry about that. Its 2WD. I just remembered that there is a '91 F250 SRW 2WD down at the junk yard. Looks like I could just grab the hubs from all 4 corners off of that and they would bolt on to my truck? Would make things go pretty easy if so.
Don't waste your time w/ that junkyard truck unless you're strapped for cash and/or it has brand new front rotors. Reason for saying this is that unlike a dually that has a hub and a rotor that bolt together, the SRW 2wd has the hub as part of the rotor. Meaning to convert from DRW to SRW on a 2wd brick all you gotta do is remove your calipers, yank off the DRW hubs and rotors, slide a pair of SRW hub-rotors in their place, and reinstall your calipers. Beware that the new SRW rotors will come w/ bearing races already pressed in them but no bearings, you either reuse the factory (SRW, which you don't have) bearings, or buy new - based on a certain trend I have been warned about by parts stores employees, you'd be wise to beat those pre-pressed races out and in their place install the races that will come w/ your new bearings... Also, stick w/ brand name bearings, like Timken or Koyo or SKF.
For the rear you can just pull your dually wheels off, and bolt the singles on. The DRW alxe is 4" wider per side than the SRW one, but the SRW axle is already 2" narrower per side than the factory bed, so your rear wheels will stick 2" out the factory bed - you can solve this w/ some small fender flares to keep the law happy, and in case of a flat bed it may not even be an issue. By reusing your DRW axle you gain wider track (for stability) than a factory SRW, and also larger brakes (SRW shoes are narrower). You also don't have to spend money on new U-bolts, which would be needing if you go about swapping the silly-narrow factory SRW axle in place of your DRW one.