JJ..here you need to be a little more specific on what you mean by Model A roadsters. Do you want to build a street roadster, gas/fuel roadster, modified roadster or rear engine modified roadster? Gas/Fuel are most common for Model A's.
Do you want it frame rails? Stock. 32 type, 2x6 rectangle steel? Do you want a multitube? Do you want to sit in the middle or off to the side?
As you see here a lot of thing to find out what you want to do...and last but not least; why a Ford model A body? Good Luck