Thanks for all the feedback. I simply could not have built this without all of the help I received here.
It was such a fun part of the project that several other ongoing projects had to wait in the wings.
The tube is standard 1.5" OD aluminum tubing. The OD is larger than an original because I couldn't get any std stock with thinner walls. The ID matches the original, however.
The main body is 1/4" thick aluminum angle with a 2" side and a 3" side.
The rest is standard 1/8" bar stock.
I'm lucky to be in the neighborhood of onlinemetals.com. Great company, great service, great prices.