Question about 67 SWB frame

[WorldsCrappiestTruck]

Adding some questionably helpful into here? I just got to stripping the frame of my ‘67 GMC 2WD short fleet and have these markings I came across.

DRIVERS
3914401-310
3-30-110

PASSENGERS
3914402-310
4-4-110

VIN tag has rosette rivets, has CS1570D on the VIN tag, CS1570-120 on the cowl, CS1570 on the inside of the drivers frame rail…..then a bunch of 507, 495, 1116 markings on the firewall. No idea what these mean.

There is also something cryptic on the inside of the drivers frame rail.

No VIN stamp on the frame anywhere unfortunately - causing me a hang of a time with the local regulators on having a VIN verification done. They’re adamant they need to see the VIN in 2 spots. All I have is the door. No SPID, no frame stamp like my ‘68 proudly shows.

I hope something is helpful here??