With a single rear axle and single rear tires, I doubt the frame is the load limiting factor, as the frame is rated to support two rear axles and 4 tires. The limiting factor is going to be the lesser of the tire capacity, axle capacity, or suspension capacity. Michelin 395/85R20 XZL tires are rated at 18,000+ pounds per tire in a single configuration at 95 PSI. I don't have data for the 14:00, 14:50 or 16:00 size milsurp tires, but I would suspect a pair would exceed the load ratings of either a single axle or the suspension.
From the Memphis date provided by Jaonjc, the 5 ton front suspension is rated at 18,000 pounds, the rear tandem at 44,000 pounds, so a single 5 ton rear axle should be good for 22,000 pounds. So your rear is going to be limited by either the axle or the suspension you hang it on. To extrapolate jatonka's suggestion, I wold derate the 5 ton front suspension to 14,000 pounds and a 5 ton rear axle to 18,000 pounds. So you would have a 5 ton front axle and suspension rated at 14,000 pounds. If you used 5 ton rear axle and front springs, you are still limited to 14,000 pounds on the rear for a total of 28,000 pounds. If you came up with a better rear suspension to support the maximum rear axle capacity of 18,000 pounds, you could end up with a max capacity of 32,000 pounds. Quite a bit better than the Deuce front axle, Deuce rear axle/Deuce front suspension gross of 18,000 pounds.
Legal disclaimer: These are not sound engineering calculations, this is a SWAG based on guesstimates of uncertain origin. Your mileage may vary. If you are going to push this to the limit, consult with a competent engineer to calculate a more definitive capacity rating.