Ozrockrat has posted some great information on tires, axle widths, wheels, offset and bolt patterns. He's also recommended some specific wheel model numbers, so you don't have to go digging. Unfortunately, none of those were in our budget. What we found was that steel wheels cost about $300 each, new, and aluminum are closer to $500.
On the Craigslist in Phoenix, we found a set of 6 9-inch wide semi rims with the standard offset. They were $160 for the set... now, that fits our budget! And a local tire shop has used "flat face" 9-inch rims for $50 each. We have two of those, for a total investment of $260. Now, it's time to try the fit.
With standard offset wheels, front and back, the rear wheels look like they'll be close to the edge of the fender well, but not protrude. It looks right and good. The fronts also fit inside the wheels, but I'm a bit worried about conflict in sharp turns - I'd used a cardboard tire profile, taped on the rim, to do some checking... it's clear that having the wheels set out a bit more would be good.
Here's what standard offset semi rims look like...
They're designed with enough offset so that the DRW can ride next to each other. Most of the "flat face" wheels I've seen are marked "steer only" because if you tried to put them back-to-back in a DRW setup, the tires would clearly rub against each other. Here are the flat face wheels...
And here are the track measurements, taken from the outside edge of each wheel/rim:
With standard offset wheels, front track width is 90 inches.
With standard offset wheels, rear track width is 96 inches.
With flat face wheels, front track width is 93.
We could put flat face wheels on front and back, which would result in identical track widths front and rear, but then the rear wheels would be tucked in about an inch and a half. From what I've read, the minor width difference won't be an issue. We'll report more when we actually get the suspension and wheel well mods done, then get everything mounted. But that won't be for another 4 weeks or so.
And, with the 19.5-inch wheel and spare tire removed, that freed up the left rear cabinet - this is underneath the future shower/toilet area. The new spare won't fit in here, so it will live on a mount above the rear bumper. You've got to love the lighting they put in these!
From another angle, you can see the vacuum pumps - these will also get removed, along with the protective panel in the front of them.