Need Help Decoding G10 Vin

The Vin number I have Starts with G1256P but can't find anything with "56"

that says 1/2 ton 1966 panel

Look at this info from VCVC (Vintage Chevy Van Club)

P=Pontiac Assembly, Pontiac MI
4=Scarborough Van Assembly, Toronto ON (1963-1993)
5=London Assembly, London ON

Here's an example 1st Gen VIN, based on a Canadian member's:

4G1205123456GA

4=1964
G=Chevy Van (unitized body)
12= 1/2 ton, forward control, might be 1200 lbs GVW
0=body style?
5=London, ON (P=Pontiac, 4=Scarborough)
123456=factory serial number by year?
GA=Engine/transmission combination, A probably means PowerGlide

Here's an example 2nd Gen VIN, based on mine:

GS158P123456

G=Light duty, forward control
S=L6 Engine (E=V8)
15=load capacity of 1500 lbs
8=1968
P=Pontiac (4=Scarborough, 5=London)
123456=sequential serial number

So as Doni says, you have a 1/2 ton 1966 (P)anel built at the London, Ontario plant, but the P could be Pontiac and the 5 could be body style?

our Chevy vans use 3 different types of VIN numbers,,,,,the 1964 is different from the 1965 and 1966 and the 1967 to 1970 are different than the other 2,,,,,,,,,