If this thread started with a question about a Canadian truck, I believe all the Canadian 6 volt GMCs were Chev chassis and thus they were negative ground. I know my Canadian 51 GMC always was negative ground and according to GM, it has a Chev chassis.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!