I had a propane powered mid-80's ford f150 pu 1/2 ton for many years. The propane tank was behind the cab. The tank was rated 114 gallons. The most fuel loaded at one time for me was 102 gallons. There is always some air space in a propane tank. A gallon of propane weighs 4#, half the weight of gasoline. The tank fit sidewise across the bed and inhibited the installation of a slide in camper. Propane connections are easily monitored because if your fitting isn't tight the fitting will freeze. In mild weather, touch is the safest assurance of tight connections. That detail is important because all that can go wrong is damage to fittings for the most part.
Many people drive their propane vehicles powered by five gallon tanks, although it sounds like clown college.
The propane carb is a vacuum chamber with a diaphram that can split with wear and is simple to replace. That's the only repair in a propane carb. Conversion to propane gets tricky about timing, not carb. The timing values change and it's all book learning from there.
If you don't know timing, don't ever mess with your distributor. Shop settings won't help in many cases is my understanding. You'll get to look at your plugs a little more due to heat. Computer issues arise in conversions, also. Many of these neg issues relate to late model vehicles in my frame of reference, to be clear on computer stuff. I cannot speak newer models. Mileage isn't great either on older models but I've heard of fair mileage on newer vehicles.
Propane burns much cleaner than gas. You can still croak the packrats but the fumes won't kill you as fast as unleaded. Also there is no slick layer of grime all over under the hood.
Buying Propane is interesting. I travel a lot on the west coast and I had developed a long list of propane sources. Propane is a waste product of oil refining is my understanding, and when they're not pumping it into trucks to sell, they flare it off to be seen for miles. That's what you're paying for.
Attendants in propane sales at small stores generally resist any notion of large propane sales. It takes them from the comfort and security of their pos. Understandable, just keep in mind when negotiating prices on the fly. Owner's often deal for bulk sales. Small stores can be difficult but well worth contacting the owner outright if you travel through regularly.
Key detail of propane retail is that propane meters rarely have calculating devices, or rudimentary ones at best, in that the attendant carries the information of the meter to the pos. Lots can happen in that short stint. Regardless, be wary that the meter total matches the receipt. Lots can happen.
Chance encounters with propane trucks doing deliveries can result in bargains if you "wink wink" are amenable to the slippery slope.
Basically there are two types of propane services available, the convenience store, and the local propane distributors. They both present distinct characteristics. The distributor will supply you with the local average price by default. Then find the small outlets. KOA sell propane, and many odd sources pop up. Mexican propane outlets are super cheap, w/no advertising - just word of mouth. Pretty soon you'll spot propane tanks like beer lights.
The convenience stores usually only fill the five or so gallon tanks and charge top dollar. Top dollar, if you wanna help hold the line against gouging merchants, should be around two dollars a gallon. Call the owner. Angle for the bulk repeater special.
The local distributor standard price can be fair, but not always competitive by a long shot. They usually have lots of the proper gear and fittings. They also know every local price and outlet. Therefore doing the legwork can result in a lot of savings. You will find propane in the same podunk town selling from $4 to $1+. Since the meters don't calculate prices, be bold and bargain. The savings can be substantial.
Another point is that a propane vehicle is vulnerable to gasoline auto mechanics. Local propane distributors always know the local repair person that knows propane vehicles. Be exceptionally wary of letting the untutored under your hood. Things are very different down there now.
Hope that helps.
"Ring your bell even if you don't sell a clam. " Samuel Clemons