That's going to be a spare tire mount for a FJ40. The hinge is what is pictured.

Bert, for the Aluminum you want to weld, it really depends on the mass of piece as to the amps you'll need. I usually save the big stuff for my spool gun, but I have welded some smaller 1/4" and 1/2" plate with my 200DX. I used 3/32" ceriated(orange) sharpened to a pencil point, 180amps, 120Hz AC, 75%balance, and 15cfh gas.

Thanks for the comments everyone.

By the way, this is a Johnny joint.