If you go by what the factory designed the bolt for you need a bolt with gross vehicle weight (GVW) of 12,000 lbs. That's 3,500 for the bolt and 8,500 for the trailer, my C20 weighs 3,500. According to my 63 manual the C30 (1 ton) with optional heavy duty springs is only rated at 10,000 pounds. The CL50 (2 1/2 ton??) GVW starts at 10,000 and goes up to 16,000 with optional springs. Beyond the spring rates, I think the big factor here is brakes. I would definitely figure putting disks on the front. I have a friend that has 1998 Chevy 2500 with big block vortech that pulls a race trailer that weighs 17,000 pounds. He is watching the traffic way in front of him all the time.
Larry
