Sorry I'm late on this one, guys.
You are going to laugh your butts off, when I tell you what I used.
Bald 235/85R16 Kuhmo M/T's on my dual wheels.
I keep telling the other guys that pulled with me, "It isn't about how much power you make. It's about how much power you can get to the ground."
I do kind of feel like a shetland pony amongst clydesdales, in here. No fancy stuff, just a basicaly stock old pickup, draggin a sled used to test antique tractors. If I got in a league with you guys, I'd probably have to get out and push.