This is the last year of this GMC/Chevrolet Carryall Suburban style, running from 1941 to 1946, mostly used for war transport.  The Chevrolet Suburban had a 216-cubic-inch 6-cylinder engine while the GMC version a 228-cubic-inch 6-cylinder engine.  I don’t think the original engine survived in this example: there is an exhaust pipe in front of the rear wheel. (But, notice that the sales brochure has artfully chopped the roof — which one is the custom?)