To answer your question, the answer is that it depends. Many cars of that era, all the way into the '60's, have two or three sets of numbers. Many bodies were built by outside suppliers like Briggs, Fisher, Fleetwood, etc. Cowl tags were usually the body number, not necessarily the chassis number. Chevrolet VIN tags (or chassis numbers) of the late '20's were affixed to the left side seat risers. On Fords, both numbers are attached to the firewall.

My experience as an insurance adjuster has shown VIN's to be in the following areas on various cars; top of the instument panel, firewall, top of cowl, top of radiator support, left door jamb, ight lower instrument panel, right door jamb, left front seat riser, inside firewall, inside glove box, and left windshield pillar.
Having not seen every car ever made, it's possible that there are other locations as well.

In some cases, the chassis number was stamped on the frame rails as a secondary number. Hope this helps.