I finally got a reply from the eBay seller. The auction carrier is for a 1/2 ton truck.

I have contacted one of the swap meet advertisers, who offered me a 3/4 ton rack for $55 plus shipping. I have sent him a money order.

Ray, thanks for the information. I didn't realize who you were till your second post here. I'm having trouble visualizing the six thick washers you described. Where do they go, or will it be obvious to me when I get the rack?

The wheels I am using have a lot more backset than stock wheels, so I will have to devise an extension to hold the tire away from the bedrail. However, the weight of the tire/wheel combination is about the same and it's only an inch or so wider, so the center of mass will be in about the same place. I don't expect to have a problem provided I get all the reinforcements installed correctly. I may be back for more help when my carrier gets here.

Thanks, all, for the help.

Joe