The center disc is really known as the "wheel" and the part where the tire mounts is the "rim". I now know that the 28 x 11 rim with 6 loops from DB Electrical will fit the wheel on the Long 350/360. The rim loops are on a slightly smaller diameter circle than are the bolt holes in the Long Wheel. But 5/8" bolts will fit though the openings and should work just fine. The loops may result in a different tire width spacing on the tractor than with the original rims with the "Z-bar" mounts.
Now we know.
The rim is from India, nicely painted and is number 3008-1015. Supposedly fits many different tractors.