David, with your skills, I don't think duplicating that Alcoa rim will be difficult!
Look outside of "normal" kit building supplies for your master, like copper or aluminum tubing for the "hoop".
The center should be fairly easy with thicker sheet styrene carved to duplicate the 3-dimensional features of the 1:1, or use rennshape, or balsa foam, etc. Some brass hardware in the proper size for the lugs and lots of patience and some time & you'll have it!