I finally finished my brew cart build, and broke it in with a 10-gallon batch of cream ale this past weekend. It's a converted factory cart I got at a surplus yard. I had a friend weld a couple custom drop-in burner frames and add some channel strut for mounting gas pipe, conduit and copper water lines.
The cart holds the hot liquor tank and brew kettle, as well as my March pump. I use a 60-qt Igloo Ice Cube as my mash tun -it sits on a small table next to the cart on brew day. All of the vessels, the pump and the high-temperature hoses (not pictured) are fitted with brass quick-disconnects. It is set up so that I can just connect an extension cord, RV water hose, and propane tank and all the switches and valves I need are on the cart - including two water valves on the mast for filling kettles, and supply to the immersion chiller. There's a third water valve at the bottom for a short garden hose used for clean-up.
All the electrical boxes are "wet-location" type with compression-fitted EMT conduit. There are two switches that switch two outlets in a single-gang box (one for the March pump, a second for a fountain pump used to recirculate ice water for chilling). There's a second single-gang box with two non-switched outlets for other electrical stuff like the drill I use for aerating with a Mix-Stir.
The cart is fitted with 1/2" black pipe, an adjustable regulator, and needle valves to supply the two 70,000 BTU burners. Eventually, I'd like to concert to natural gas - but that will be a while in the future.
What an improvement over the Rube Goldberg setup I used to set up and take down every brew day!