Thanks for all the comments!!
After fighting with this frame time and again, I finally took some of my son's Legos and made a jig to put this frame together. It is finally straight! The air ride minus the bags and rear axles are installed thanks to the help form Sean "Old buckaroo". R model springs were used on the front. The frame on an R model gets wider at the front, but on the B and H models it does not. After installing the springs, the Mack front axle from both the AMT kit and The MPC/Ertl kit were slightly too wide at the spring perches. Since this is a custom, I installed a Road Boss front axle with poseable front wheels. The engine is 85% together, the transmission will be a 4x4 Spicer. A 4 speed auxiliary is mounted as well. I'm casting tank mounts and brake chambers. It seems that I didn't have as many as I had thought. The wheelbase is right at 270" in scale. Still a long way to go!