My RT grove crane is right around 67-68,000 and 10' wide. I haul it on a 3 axle truck and 3 axle double drop detach trailer. I have a 25' well. At my length, the extra axle of a 4 axle tractor, only gets you another 1,600lbs gross allowable on a permit. The extra axle weighs more than that- so a 4 axle tractor doesn't give you any advantage. I'm 41' axle spacing, so could get up to 118,000 on a permit, and I think I'm under 105,000 gross.
I looked up a 973 and they show between 60-70,000 lbs for a 973, there's no way you are getting under 80,000lbs gross. Truck is going to weigh 18-22,000 and trailer 15-18,000 so you're going to be 100,000 or so.
Three axle truck gets you a lot shorter truck which really helps making corners and driveways. A local dirt contractor has a 4 axle sleeper truck and its a huge pain, and doesn't haul any more legally than mine, unless they put the rear stinger axle on 8' behind the trailer axles.
Your trailer must be a single drop tandem to only be 12,000lbs? Aren't you overheight? Are you really short on the trailer? I was going to suggest a single drop tri axle but I didn't think you would be under height.