All Classified forums require a Site Supporter subscription. It is only $25 per year and you can buy and sell whatever you like on the forum. To become a Site Supporter, go to Your Profile and select "Paid Subscriptions."
Here's some 18s with 35" rubber on a 66 if that helps...
I think it would be a more practical rig than some of these truck with carbed bigblocks 3 speeds and massive mudders. Besides, 99% of the time the truck is on road so why not design it around that fact.