Paint: 2603 Code for the paint color -- Canadian built 56 Chev's paint codes are the same as the Canadian built 56 Pontiacs except the Chev first number is a 1 and the Pontiac is a 2 -- 2-tone combinations used to be shown at this source: http://www.classicbowtie.com/1955-1957%20Chevrolet%20Canadian%20Cowl%20Tag%20Information.htm-- looks like that site has vanished into the ether, however I searched a while and came across this:
If you scroll down a bit you will see that your 2603 = Sherwood Green Metallic over Pinecrest Green(interestingly, my car's original color was the color of your roof, Sherwood Green Metallic) -- and that sure looks like the colors on your car now.
Body No:1311 Your car was the 1,311th 4-dr sedan off the assembly line
1956 Pontiac Pathfinder 2dr sedan, 496 - dyno'd 545 hp, stick shift, 4.11 posi - Hot Rod