Thanks Bill,
That being the case, another way I could still save a few bucks might be to find a cheap set of original 16" drop-center wheels for their centers, and weld a 6" wide later rim to them for the offset & width I need. I think the rebuilt wheels would be about 4" larger in diameter than I can swing on my lathe, so I'll have to come up with an alternative way of checking true after tacking them up, but I can figure that out.

Thanks for the help guys. If I come up with a simpler solution I'll post it. Otherwise, when I obtain the wheels/parts I'll try and put together a photo stream of the conversion and post it here for others that might be interested in building their own set of custom wheels.

Best,
Phil