Yes, the Airlift kit comes with two valves ... I assume the Firestone does as well. As already mentioned, there are many options for mounting them. I have the valves routed to each wheel well ... just above and to the rear of each tire. There is a hole there just below one of the truck bed...
I would skip the airlift compressor to inflate the bags and save the money ... it's a one trick pony for the airbags only. I skipped this option, plumbed the bags independently so I can adjust the bags as required for level left-to-right, and spent a lot less money for a portable Viair 400P...
Yes, I drilled a hole in the rear, driver's side bed and installed the OEM plug that I purchased from the dealer. It came with instructions for measurements and a template. It's aluminum, so it is easy drilling. Looks just like factory.
You will almost certainly be over your stickered GVWR ... just know that beforehand. Cirrus 820 will probably come in about 3600-3800 lbs wet weight. Search this forum for a member named Uncas. He had a Cirrus 820 on a derated F350 Tremor. His wet weight was just north of 12,000 lbs. You will...
Electrically, yes. However, you cannot physically insert both connectors at the same time without totally removing the spring-loaded cover on the 4-flat. I installed an OEM bed connector (fifth wheel option) for the truck camper to accomplish what you are trying to do. Cheap and easy install.
Check lower shock mounts ... the shock may have the slightest play which is hard to detect until you are driving and hit a bump. I really had to torque down my aftermarket 5100's on the front.
I looked hard at the 820 and Northern Lite 8-11. Ultimately, I went with 8-11 (dry weight of 2750) because I think NL does better at giving an accurate dry weight, as built. I think the Cirrus 820 is a just a bit heavier than published (not a fact but just my thought). Another member on this...
4000 lbs of payload goes quickly. I've had two truck campers and the safe bet is to add 1000 lbs to any listed dry weights to get a wet weight. And MOST, if not all of that weight, is on the rear axle. I have a Tremor F350 (XLT / 7.3 gas) with 4012 payload with a Northern Lite 8-11 (dry weight...
Torklift Upper Stableloads (part # A7200) with their 1 1/4 inch extensions (part # A7201). They engage the upper overload springs before camper is on the truck.
I do have airbags but only use them now to lift the truck for installing stable loads and then drop them back down to 5 psi (left) /10...