rock331 - The info on these style grille and radiator guards is definitely difficult to find. Here's what I could find searching through multiple resources and some additional web searching.
Chevrolet offered GM Accessory Grille and Radiator Guards for 1947-50 AD series trucks. One for 3000 Series pickups and a 2nd for 4000/5000/6000 Series big trucks, both of similar design and installation. You can see drawings of these particular style of guards in the 1st attached picture taken from a 1950 Chevrolet Accessories Installation Manual.
Chevrolet offered a revised set of bumper guards for 1951-53 Chevrolet trucks. There was one style of guard for 3100/3600/3800 pickups as seen in the second attached picture and a newly offered Commercial Truck guard that looks similar to your pictured guards for 4000/5000/6000 series trucks. The third picture is from a 1951 Chevy Truck Data Book and shows both styles of these guards, while the forth and fifth pictures are from some Chevrolet advertisements I found on the web.
A third redesign of AD Series bumper and grille/radiator guards came around in 1954-55.1 trucks. The 3 different style are in the final attached picture I snagged from a 1954 Chevrolet Truck Sales handout.
Based on this info, I don't think any of your 3 different guards above would have been original GM equipment.
Just my $.02 worth, but here's my take on what you have:
Your first guard appears to be a possible period aftermarket or home made replication of a Big Bolt style guard, but possibly sized and outfitted with the 3 point bumper bolt mounts associated with 3100/3600/3800 truck guards.
Your second guard appears to be a replica of a Big Bolt guard, again either period aftermarket or home made. Can't tell from the picture if this would fit a pickup or bigger truck.
Your third guard appears to be a home made replica of a Big Bolt style and size guard. Perhaps an early aftermarket piece, but look kinda roughly formed/fabricated to be a commercial product.
Hope you find this information helpful.
