I've been mostly just figuring out what I can use for parts so far. The ATV wheels I was going to buy are apparently discontinued and no longer available, so I picked up some 8x6 trailer wheels with a 4 on 4" bolt pattern. They were way more expensive, but they came with tires that I can use on my boat trailer, so figured that was worth it. I picked up bearings for a 1" axle, and some other stuff like sprockets and hubs for them and my brake rotor. I was thinking of building my own wheel hubs using split tapered hubs to keep them tight on the axle, but then I found these go-kart hubs in Canada for what looks like a decent price.
http://www.kartworks.ca/index.php?main_page=product_info&cPath=198&products_id=1229Would they be strong enough for racing on a fairly rough surface? They'll certainly be lighter than what I was thinking, and require less fabrication. I mounted one of my new tires to check the diameter, and they're 15.5" inflated to 15 psi. I need 5" of clearance to the chassis, which is 2" tall, so this means I'll run my axle above the chassis and not have to notch anything. If I ever switch to smaller tires I'll have to change things up, but I'll cross that bridge if I ever get to it. I've decided I'm going to use the chassis pan from the Craftsman. I can reinforce the frame in basically any way I see fit, so I'm going to weld some reinforcements to the outside rather than the inside like most do. I got the pan all cleaned up today and came up with a bit of a plan at least.