The replacement ones are not the same. They are a machined pulley not stamped steel. I had to cut the cap off the old pulley to salvage the special bolt.
We did a similar trip years ago and stopped at bed and breakfasts along the way which were recommended by the local tourist centres. We stayed at some wonderful places, and had a great time talking to our hosts.
Did you try European cars with a 5X100MM bolt circle? Volvo comes to mind. I believe that is close enough to 4 inches for a temporary spare, but you might get away with chamfering the lug holes a bit.
I found a spare from a Ford Edge. It is 4.5 bolt circle and the tire is 27 inches in diameter. It fit nicely in my B-body trunk well, I'm not sure about an A-body though. I did have to open up the center register a tad to fit over the axle stub.
If you are looking to have your torque converter redone Steve, I used J&K Torque Converters in New Hamburg and they did a great job. They can adjust the stall speed for you within reason.
I made the same two changes with mine. The tip in at part throttle is where the power valve helps, and it cured my flat spot. I'm not sure they make anything higher than a 10.5 anyway?