Hi Gordon -
I too was confused as to who the OEM actually was/is for those things, but I ended up going with rvupgrades.com because they're one of the sponsors of this website
I think actual dash-placement depends a lot on where you can see the display. I initially had mine way low, such that you'd have to turn and tilt your head to see it. One day, this loud beeper went off and I immediately checked all engine/trans functions, etc. Finally realized the PP was blinking, but it wasn't obvious to me at first where to look. So it got moved right up under the dash-top lip. Nice to periodically check pressures while driving too.
Depending on your situation, you may have to use their extension antenna or the repeater if you're pulling a toad with sensors too. I'm 40' and I had an intermittent signal from the toad, so I ran the antenna cable underneath and mounted the antenna just forward of the rear-axle (mostly because that's how far the cable reached) tilted downward a bit. As it is, I still sometimes lose the RR tire-signal from the car.
I hard-wired mine by picking a lead off the dash-radio supply. It draws little current so there's not much of an additional load.
I would definitely recommend switching to steel-stems on a toad if you're using 'em there too. Even tho PP says the sensor weight is minimal, it's probably enough to bend the rubber stems enough from centrifugal force to cause problems.
I feel so much better driving with the sensors. I occasionally get low-pressure warnings first-thing in the morning when the tires are cold, but they heat up quickly. And with 400hp up front, I know I'd never see, hear, or feel a tire going flat on the toad til I'd see sparks coming from the car as I dragged it along on its rims.
I too had a bad sensor and they replaced it pronto. Even sent it on ahead to meet us at our next destination.