In 1940 there was no internationally recognized standard for VIN numbers, and each manufacturer basically did what they wanted.

So unless you have a title that has a number from the truck represented as the VIN you can't say it has a VIN. If the tag is still in place one of the numbers should be a serial number. If it were me I'd try to use that number to get a title.

Its probably the number that starts KF that you mention, though I don't know Chevy serial numbers for '40 and could be mistaken.

However, you need to jump through whatever hoops your state has to do that. Joe's link should help with that part.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...