Jim and Jim
i would start with tank size, then compressor and then go from there. Those are the two hardest to install and costly (compressor/s).
On the long bed Fords you can easily put a 5 gallon tank above the driveshaft, without removing anything. It does take some fabricating of brackets. You could probably get an 8 gallon up there.
I have a 5 gallon above the shaft and a 3 gallon (came with the suspension kit) under the right side rear door.
Keep in mind, many of the compressors are rated at 5 gallon max tank size.
I have pull cord tank drains on each tank with the cords next to the right side running board. Sometime before the winter I need to add a cover for the lower tank to protect that valve from snow and ice.
You can't have too many ports on a tank. 6-10 ports may sound like a lot but it really isn't if you need a low point drain to be forward with the brackets on the left.
i have a heavy duty 200 psi 100% duty cycle heavy duty compressor. Although fairly large and with a built fan and heat sink I am a little disappointed with it. Just too slow for the cost. And the wiring, that you are not allowed to alter is under sized. The supplied relay, which you are also not allowed to alter for warranty purposes failed due to moisture within one month.
I am using a ViAir regulator for the truck and hitch air bags, regulated to 110 psi. Besides the bag requirements it cuts down in compressor cycling.
Jim M, I would consider mounting the compressor/s in the bed under your tool box.That would offer weather protection and may cut down on the in cab noise. My compressor is on the chassis and quite noisy.
If I were to do it again I would get a pair of ViAir 200 psi, 100% duty cycle compressors.
I would run 6 gauge wire from the battery to the compressors, fused at the battery end.
I would use a marine rated heavy duty relay (automotive starting type).
A resistor and diode across the terminals maybe to hopefully stop the "pop" I get in the radio when the compressor kicks off.
I use both a 150 psi and a 175 psi switch for the compressor, selectable in the tool box.
150 is for everyday use. 175 is for filling the cyclone tires. Most pressure switches have a 35-40 psi differential between cutting in and off. The Cyclone tires are filled to 115 minimum, so the 110 psi cut in is a pain.
All wiring, connectors, fuses, posts, relays etc are marine rated from West Marine.
Most of my airlines and connectors are from Michigan Spring. I have a brass bulkhead connector in the trucks trailer hitch that is my tap for an air hose. That connector is actually a WM fuel line item.
Some items are from Amazon like 1/4" 1/4 turn valves, I use that to shut off the air to the hitch when removed
Wherever you mount the air horns I'd suggest mounting the air relay as close as possible, even directly on the horn if there is room. Having the relay at the horn will eliminate the delay of getting max psi air into the horn. My current relay on the tank has a noticeable delay for the horns.
I tapped into the electric horn circuit (at the horn) and ran a 12 gauge wire through the frame up into the cab to an on/off switch next to the 12 volt port. This gives the option of electric only or electric/air horn.
Air tool usage will probably require a 3-4 CFM at 90 psi compressor. Just not going to get that affordably for the trucks. You are looking a $1k and up for that in 12 volts.
I use a Snap-On 18 volt impact for the roadside stuff.
By having an airline and nozzle at dog camp I was able to save two iPhones that got dunked!
blew air though all the holes until as dry as possible then put the phones in bags of rice. 12 hours later the were good to go.
