There are many differences between the 39 and 40 models. The 39 deluxe looks similiar to the 40 standard and the 39 standard looks very much like the 38 deluxe. On all 39's the windshield opens up from the bottom for ventilation(also great for water leaks). The windshield wipers also mount on the roof just above the windshield. The doors on the 39 do not have vent windows. The one piece glass rolls back before going down to allow for ventilation. The dash in the 39 looks very much like the 38 and the 39 has the floor shift. There are many other small differences from the 40 , but these are the most obvious.
The 40 has a fixed windshield with a rubber seal and the wipers mount on the cowl. The 40 has vent windows(windwings) and the dash is totally a new design. The 40 has the column shift.
If you want a good book that will show you the differences you should purchase "The Early V-8 Album" put out by the Early Ford V-8 Club of America. The album shows every Ford V-8 from 32-53 and shows the differences and gives the production numbers for each year and body style. You can order the book by calling 707-226-5256 between 8:00am-8:00pm PST or by e-mailing;
[email protected]. I think there is a sale going on the V-8 Album