I have a bunch of these door checks for IHC. I do not know how many we will need for our two projects, plus a few spares. There is the regular "L" for and with my daughter and a four door "R" crewcab.
Bob Drake Reproductions sell sets for old Ford cars. The Ford units are very close to the IHC units. There are two lengths from Ford. Buy the longer 4.50" ones. This is where the longer Ford units are a good choice.
The original IHC restraints are 4.74" long. I will measure later when I get out to the shop.
If you chose to make your own door checks it should be easy enough to make something in your shop. The restraint has a slight curve. The heavy spring catch and hold may not be so easy to make. Ford never used the catch and hold and I have only needed that function a few times. I have used a Vise Grip on the restraint to hold the door open. This can be a damaging situation if someone closes the door before removing the Vise Grip and it get in the way of closing.
https://www.bobdrake.com/FordItem.aspx? ... 6c6c39293e