Ok, Ben.

That holder is a clamp of sorts. The little round "eye" on top is a screw that tightens the top plate onto the lip of the gas can as it turns. On the back of the aluminum piece was a piece of U-channel that I thought was cheesy, so I ground it off and welded a piece of one sized pipe to the plate that bolts to the tire mount and a larger size pipe to the plate that mounts to the "clamp" assembly. I then slipped the small pipe into the larger pipe and drilled a hole all the way through so a pin can be put in to make a quick release for the clamp. That made mounting the spare easier and I'm able to put other "attachments" on there with the right size of pipe.

Anyway, more info than you asked for, but there it is...