I'm with the posters above. If you can find an affordable straight axle set up, go with that. It will provide the cleanest and most traditional look. However, keep in mind that your total cost may go well beyond the pieces you find at a swap meet. As Pasadenahotrod mentioned, you'll no doubt want to upgrade that old 30s/40/s straight axle with more modern brakes and spindles and if may also need other upgrades as well.
Also, being HR.Coms resident twin I-beam junkie, I can't pass up the opportunity to plug the Ford setup. There are a zillion of these twin I-beams out there in the bone yards, they are inexpensive, and they come with modern spindles and disk brakes. Here's how it looks under a full fendered car and also a fenderless car. Just another option to consider.