I was off a little on the 12.22/5s if they are 7400 a tire than 13320lbs on that axle would be 90% of max.
I regularly put 12000lbs on 11.22/5s, the next size down, on the steers on my Peterbuilt. They have always preformed flawlessly.
I recently had a discussion with Jon about the preferable cost and availability of the 11.22/5s combined with my current axle weights. When tire time comes I might very well size down thus being able to rotate out dated tires over to the truck before dry rot sets in.
I don't mention this to convince you to do this but to give you more confidence in your 12,22/5s.
I have 2 sets of shocks up front but have not experimented there yet. Prevo Parts in Elgin carry them and have a prt#.
Many have upgraded to kona shocks. Harry really spoke highly of the switch.