Tow rating, GMC Topkick

I have a 90 GMC Top Kick 7000 28000 LB GVWR. It has Caterpillar 3208 Turbo V8 Diesel, air brakes, Allison transmission. I'm considering a 31000 LB excavator. I'd move it a few times a year, over near level road at 20 MPH. Can I do it?

Tow rating, GMC Topkick