These a often called Chicago Rivets or Screw Backs. I got nickel plated brass ones with a 8mm-5/16" head diameter. They just screw into themselves making riveting leather easy. Strap can be wrapped around a bar for instance that is already welded into place. I have got it on back to front to make it easier to work out the length I need to make the strap.
Works really well and this mock up strap will work as a template for when it is time to do upholstery. I'm actually trying to find another one of these belts that I used to have to make the strap from in the final version or will make my own as prefer to have Willys stamped on it.
Been nearly 2 1/2 years since I stripped the paint off the grille parts and ran them through the citric acid bath to remove any rust before spraying with lanolin. Glad to see that it didn't rust sitting in the garage in all that time. I am starting by adding an extra grille slot on each side by using a bigger centre section cut from another grille to do it.
You face little problems like this with the top face not matching up due to the taper. After welding all except the turned lip on the inside, I will refold the wider part to blend in with the rest. The stake I'm forming it over is some 16mm steel from a towbar tongue and fits inside, so will hammer along its edge.
The blend worked quite well. The lip on the inside was trimmed so it all was the same length. So this is the first part of the widening as this only added 5" and need a total of 9" to match the extra width of the cab. 2" on each side will be added between the headlight hole and the side of the grille. The slotted area of the grille matches the donor Grand Cherokee radiator core width. The extra 2" each side will have the tanks behind it. On the wall above on the left is the original 1948 grille and the one on the right in the 1958 grille. I have been shooting for a blend of the two styles.