David
What a gem . It is a No. 11 cab and it's in very good shape - believe me.
There are a few of us on this forum with C8's . Myself, David Pope in Canada, Andrew up at Dubbo in NSW . A guy in California Dennis Deck , but he has dissapeared .
Nick Bullock in Yorkshire has one too, it was measured up for the 1A2 body plans .
The 1A1/2 body you need , not 1B , you will have to build a replica. The plans are available
From my research, they used a civilian front 'I' beam axle from the 1940 Civilian 3 ton truck - the part numbers are same .. But they adapted the lighter brakes to the axle .
The rear axle is the 1940 civilian 1 ton truck axle .. same springs , 4.55 -1 ratio.
My article is here :
http://www.geocities.com/vmvc1au/8cwttwins.html
Glad to see you chose the GM version ... the inferior Ford version would be too difficult a job ..
Mike