Semper Fi, jarhead.
Part, if not all, of the cause of your problems is the size of the tires.
Bigger tires and rims are just simply harder to balance. Bigger tires and rims means more weight being thrown around.
If I were you, I'd skip the spin balance and lead weights.
Make sure the tires are mounted on the rims properly.
Make sure the rims aren't out of round, bent, or otherwise jacked up. This, in my opinion, is where a spin balancer machine comes in handy. And you don't even have to turn it on. Most of the balancers have a little "finger" attached to them to use to give your eyeball a stationary reference. With the tire/rim mounted on the balancer and spinning a little, move the "finger" up close to the edge of the rim. You'll be able to see if the rim is wobbling as it rotates.
If all that checks out good, go to a semi parts house (like Truck Pro) or a semi truck dealership that has parts, and buy some Equal balancing media. It's a powder that comes in a little bag. The bags are sized according to the size of the tire they'll be used in. There's a chart included with each case of those bags, and the bags are sold individually. You'll have to break down the tire to get the bag into the tire. Just put the bag in, DO NOT open it first. The rotation of the tires will break the bag open, releasing the powder. The powder is re-usable, so if you have a flat and the tire has to be broken down again, be sure to save the powder and put it back in, otherwise just buy a new bag.
With Equal installed, every time the tire starts to roll, it gets rebalanced as the powder is distributed around the inside of the tire.
I've been using Equal in the tires on my semi for years. Works great, like it allot.
