Well, I'll answer two of your questions, at once:
jerem0621 wrote:
5) I run Simulators on my factory steel wheels. I can check my front tire pressure without removing the simulators, and the outer Dually, but the inner dually is impossible. Can I run "valve extenders" successfully for the inner dually tire?
6) Should I have steel valve stems installed? Currently there is regular old rubber stems. Seem to be ok too.
I just recently learned the hard way, that valve extenders can be bad news. Had one of the solid U shaped extensions (on the outer dually) come loose and leak out all the air. Got to campsite, found one tire almost completely flat. Was NOT fun.
Some use them (extensions) for years and years and never have problems, but I'm here to tell you from personal experience, they can leak, and did for me after less than a year. And, that was a solid valve extension that leaked, not even one of the braided ones.
My solution, and what I highly, highly recommend:
Dually valves. I just put a set of these on our Motorhome's dually tires, and they are great. Solid, one piece valve replacement for all 4 dually tires that will never leak, period. Easily access valve for both inner and outer dual without removing the simulators.
If you're fixing to replace the tires, thats the perfect time IMO, to put these on, since they have the tires off and are probably going to replace the valves, anyway.