Also look at Host if you are looking at the Eagle Cap models. If you are looking at used, add the Chalet to your list. The EC, Host and Chalet models have their floors above the bed rail which makes for a flat wide floor and less climb into the bed cab over. The Lance floor sits above the wheel wells giving it a lower over all height but 2' narrower floor and more climb into bed.
At minimum, you need a 3500 series DRW truck. If you plan to tow behind the camper consider going to a 4500 or 5500 series truck to get sufficient payload to handle these campers and the the additional trailer tongue weight sitting on a 3-4' extension.
2012 Interstate Car Carrier ICC10220TA3, 20'x8.5', 8" I-beam frame, dual 5200 lb 4" drop torsion axles, Diamond plate, Towmax 225/75R15 LRE tires on galvanized rims, Harbor Freight 10k lb equalizing hitch, Camping World vent cover, LED lighting, 3' RV door, front and rear door interior light switches, interior plywood walls and floor, 70' of Harbor Freight E-track rail with recessed corner 5k lb D-rings, Dual 42 gal fresh water tanks with Harbor Freight transfer pump, portable dual Harbor Freight 45w solar arrays, 100 lbs LPG in four bottles, PowerArmor Max Solar 5-battery box, Deka 24HR3000 sealed batteries
2015 Ram 5500 HD 4wd Tradesman 60" CA, Crew cab with 173.4" wheelbase, 19,000 lb GVWR with 26,000 lb GCWR, Cummins I6 6.7 liter diesel with chassis cab tune 325 hp @ 2800 rpm and 750 ft-lb @ 1700 rpm, Aisin AS69RC 6-speed automatic, Borg Warner 44-47 manual transfer case, 14.5k lb Dana S14-111L limited slip and 7250 lb Magna Steyr 275mm with 4.44 ratios, Palfinger Badger low sill flat bed, Dual DeeZee 36x18x18 under bed boxes, Quad DeeZee 48x18x18 above bed boxes, Curt Double Lock 30K lb gooseneck, Dual 3/4" horse stall mats, SuperHitch Magnum 30K dual receiver with 42" SuperTruss, Upper StableLoads, Short range FastGun turnbuckles, 10 Deka 24HR3000 sealed batteries
2018 Host Mammoth 11.5, Polarized dual pane windows, Powered and lit awning, Swing out Rieco-Titan jacks, Fantastic Fan in cab over, Aero-Flo vent covers, 3x160w Zamp Solar with 30A controller, External 24" TV with DVD, Cargo slide tray, dual 6-volt batteries, 2.5KW LPG Onan, External LPG connection, 2-way water heater, Therford 3-burner cook top, Convection/Microwave, 8 cu ft 2-way Norcold Fridge, Loveseat with foot rest, U-shaped dinette, 1000W PSW Zamp inverter, King Jack amplified OTA antenna, 40" Samsung UN40J5200 smart TV in living room, Electric heater fireplace, Accordion bedroom door, Full wall passenger-side cab over wardrobe, 32" Samsung UN32J5205 smart TV in Bedroom