Ok Here is a bit more info, I had some of it wrong from before.
6 is be the number for series, which in your case is a 60, & 8 is the wheelbase, 175". 03 is for body style or model, Cab & Chassis.
I just don't have any info on the Canadain trucks, and took a wild @$$ guess by using info found here:
1960 - 1966 Canadian Chevrolet & GMC VIN which only covers light trucks.
so your brake down should be:
6 = year 1966
T = 72" Tilt cab
9 = GMC
6 = series, 60
8 = wheelbase 175"
03 = model, Cab & Chassis
6 = inline 6
50405 = serial number
E = GVW class
GVW class is juct that, the higher the letter, the heavyer the truck. 1/2 tons are A, 6000 lbs or less, 3/4 & 1 tons are B, 6001 to 10000 lbs and so on.
Your truck would be about the same as a US Built GMC L-4000, which have a gvw class of E and are rated for 19500 lbs. Did you check out the info on my site on
GMC L-models ? also see the
GMC 3500-9500 Year & Model Information page too.
Hope that is of some use.
