I have 354's in my 1939 pickup and really like them but if you don't have much power it takes a few more RPMs to get going in first gear.
Those gears in the trans are to high for a 3.54:1 rear gear. I ran a lower gear in my 39 sedan with that rear end gear. Worked real nice with a stock and hopped up flathead. -Danny
Ok word of caution, If you killed the U joint before it was due to lack or incorrect lubrication. That grease fitting at the clamshell of the torque tube is not for wheel bearing or chassis grease. Your u-joint is liquid lubed by a splash system. The better lube for your u joint is a high viscosity liquid lube, Ford called it "soda soap" it was made from a concoction of oil and a thickener. Today the closest thing to it is John Deere "corn head grease" or just that regular 600W weight transmission lube form a Model A. Your U joint needs to be fulled with about 4-6 oz of liquid lube and you are good to go, make sure that you have installed new gaskets. This lube also makes sure that the upper roller bearing is lubed as well as the speedometer gear. Some people say that you just fill the cavity with regular grease but this is incorrect. Once the u-joint starts spinning it just creates a cavity inside the mass of grease and nothing gets lubed until the friction temperature rises enough to get the grease over heated and flowing, by then the damge has started.
The Jalopy Journal
