Thanks scrapdaddy and Ol Yeller for your thoughts and help. These are exactly the brakes I've been considering. My tow vehicle already has the a brake controller wired, although I still need to check that it actually works. I certainly don't want to mess with the tongue, so it seems like electronic is the way to go. In addition, I like the idea of having greater control over the trailer from the cab. I'll order the stuff and update as I install.
Meanwhile, I worked a few hours this morning on the 55. Still working on that wheel well. Welding on the union of the wheel well and the metal I added (which was just a little thicker) I was able to see how differently my mig welds just by adjusting wire speed. I kept the power dial the same and just messed with the wire speed. Wow, I could go from very little penetration and forming mounds of metal globs to complete blow through with about 30 degree turn of the wire speed dial.
Onward!