Upgrading front axle westernstar

So I have decided (for a few reasons) and number one being I over load it all the time. The factory front axle is a 12k and the springs are also 12k. I need to upgrade to something along the lines of a 18k or 20k axle and spring combo. The truck was originally an OTR truck that has been converted into a dump truck. So far is been a great truck being as that I am in NC it being a 3 axle truck I can only run 54K gross and that's fine. But at the same time when I get loaded to that 54k the front end is weak and doesn't handle the curves very well. So I want to upgrade it I have attached the data plate of the front axle that is currently under it. Also I know that I will need to upgrade some other parts like steering box and most likely pump as well. I also know that if I go all the way up to 20k I will most likely need to upgrade to a double box set up to.

 

I 100% agree frame flex is definitely a problem my ultimate plan is to upgrade the frame as well ultimately I would like a 20k front and 20k drop axle and double frame but upgrade as money became available