Not to get too personal, but how big are the 2 of you?
If you are over 5'10" or `220, you will want a bit more room than is common in the 20s cars. It can be done, just more work.
Another thing is that with the economy and even before, you can buy a done one cheaper than building it yourself.

Go to some rod events and agree on what works and what doesn't, and check prices of complete cars.