I made a 3-D model during my lunch break today to help me with making this thing. Check it out - it's a little different than yours and it doesn't have the third support on the top angles. It's to scale, but since I haven't actually gone outside and measured the mounting points and available space, it's not exact - I went by your dimensions.

I also used 2.25"OD x 2"ID aluminum bar, with two short 3" rods on the ends, with two bolts each for attaching to the 3" x 2" angle. The 3" rods keep the large bar in place, while the pin holds it either up or down. I'll throw some o-rings between the long mounting bar and the side of the basket to keep it nice and tight.

The hardest thing will be finding a pin that will hold still during off-road driving.

Anyway, here it is...the first pic is how the assembly looks when up:


And then how it looks down:


And a wireframe view of the pin/rod connection that allows the rotation:


And how the assembly comes together:


You can get all the parts (36" tube, 3" rods, and 10" angles - all aluminum) cut to size at onlinemetals.com for a total of less than $50.

I'm going to make sure my lights can mount to a round bar, and if so, I'll start ordering!