Fender Screws Mounting Block

When I took my front end clip off a while back I was missing one of the screws that held it on. It is a type that is not common, at least not to me. It looks like a cross between a machine screw and a wood screw with flattened threads, these are the ones that are received by clips in the sheet metal. Is there a source for these?

The other missing item was one of the front cushioned mounting blocks for the grill. The remaining one is a thick rubber cube . I 'm looking for suggestions on what to make it out of or who might sell replacement I do have a piece of thick plastic ''Trex'' deck board that might work. I often miss the obvious so I thought I'd put this out there.

The bolts a typical body bolts, go to Napa or Oriely and match them. The cushion is the same stuff they use on muffler hangers or equivalent.

A picture of the screw would help. I think I know what you are referring to, but don't know the name. I checked in my "Standard Aircraft Handbook" to see if they might be used in aircraft, and therefor their name and AN number, but no luck.
The one's I'm thinking of have a very coarse blunted thread, almost like a Acme thread but not quite. Used like Dzus fasterner.

pic

No, not what I am thinking of, these are "screws" for panels that need quick removal, the screw portion is often "captive" in the panel to be removed and are threaded into screw-plates attached to the main part of the truck. I know there must be a name for these, but don't know what they are called.

CB, I think the screws that go on the cab side have welded nuts on the back side.

Old IHC most likely did not make any of the fasteners they used. Back in those days there were many fastener makers. One of the only survivors that likely supplied IHC was https://www.auveco.com/
The on-line catalogue is very good.
Another good source for fasteners and clip nuts is https://www.fastenal.com/

It was a long but productive day in the garage tearing down my front axle (bad brakes and knuckle bearings) so I didn't get a chance to take a picture but I will post one tomorrow.

The screw in question is one of the ones that you have to reach into the pocket on the lower side wall inside the cab to remove the fenders or front clip. They don't go into welded nuts but into steel clips that slide over the holes in the fender lip. I'm surprised they hold as well as they do!

Picture coming soon!

I'll bet you are talking about the famous 5/16"-10 tapping screw! At one time you could buy them on eBay, but I don't think I've seen them available for a while. You can still get the J-nuts from Auveco. These screw/bolts are also used on the running boards.

Maybe these? https://www.ebay.com/itm/50-Qty-5-16-18 ... 0008.m2219