steering wheel seen on eBay
 

http://cgi.ebay.com/WWII-18-Wood-Ste...item4cf88b2212

It says it is 18" diameter, cast spokes and hub, says it suits CMP, CCKW, DUKW, G508 and G506. I didn't think all of these used the same steering wheel, but perhaps the seller just means it will fit.

Given the $400 buy it now, I don't think the reserve will be at a level I'm interested in paying. (OK, you can call me cheap if you want.)

Interesting
 

I note it's a rebuilt steering wheel, no wonder he wants $400 for it with all the work entailed. Note the hole in one of the spokes - perhaps for a helper knob to make removing your thumb at the knuckle easier.

I had stopped reading very carefully after seeing the price.
Did DUKW wheels have spinner knobs for their marine function?
After seeing some of them come apart due to weathering, I know that the CMP wood wheel with stamped metal spokes did not have the metal reinforced rim the seller describes. Those wheels had a rim made from a group of segments finger jointed together to make the circular part.