Don't take chances with the old axle by welding on it-get a new FORGED axle from ChassisEngineering in Iowahttp://www.chassisengineeringinc.com/forged-i-beam-axle-front-end-kit-1935-1940-ford/
You could use what ever wheels, etc you have and could weld or modify the axle if needed since its a forging-other companies are cast iron and I wouldn't weld on them