Looking at the factory manual in Section 10, Sheets 3.00 and 3.01, I don't think the brackets themselves are any different. They are reversed, but that is not a problem. What IS different is the plate with the three studs - the 3100 has them in an equal triangle for a 6-lug wheel, while the 3600 has a different triangle shape that fits the 8-lug pattern. A machine shop could probably make you a copy fairly easily. The studs themselves are standard fine thread, and if you play with the way the bracket bolts to the vetical bed rails, you can shift the mount up or down a little, depending on your tire size. Mine, with a 215/85 16, is about 1 1/2" above the running board. Hope this helps.
