1st pic body identification plate
2nd pic 13 lb pressure cap. with a/c it would have been a 16# cap
3rd pic vin plate with eng ser #. my 64 GMC panel also has the eng ser#, but never seeing the orig I can't say. my 32 Chevrolet had the same and it was also on the registration papers. the 5th digit after the C is an 8 for 8 cyl
4th pic is your GVW rating of 7500 lbs
5th pic my green 64 GMC panel had a green painted floor. my 66 ambulance had a white painted floor. still have some whhite painted ones like new as they were covered over from new
ron