If you are going to build your own frame, you can do just about anythng that you want, especially if you are not going to run fenders. A good rule of thumb is as follows.---Build the body any way you like, don't worry about wheelbase, or motor size. Get whatever engine you will be running, complete with transmission, waterpump, fan, everything you need clearance for from front to rear. If you want a track roadster style, you will have to determine if you want the body on top of the frame (highboy), or if you want to cut out the floor and lower the body down over the frame for a lower (channeled) look. The oilpan of the engine should never be closer than 6" to the pavement under normal situations. Set the engine up with a 6" spacer under the pan and the top of the intake manifold level, block the body up to whatever ride height you want it to be at, and slide the body up against the back of the engine. If the bell housing or transmission interfere with the firewal or floor, fire up the torch and cut them out (preferably a bit at a time). If you can, you should avoid a recessed firewall, because of the leg room issue. When you have approximately 1" between the firewall and the rear of the engine valve cover (or distributor if it is a rear mount distributor), stop. Allow about 4" from the front of the fan blades to where the front of the radiator will be. If you are using a model A or a 32 grill shell, the rear of the grill shell will fall just about in line with the front of the fan blades. This should also be the line which positions the center of the front axle. The rear axle can be positioned where-ever is estheticaly pleasing to you, but keep in mind that anything less than 104" wheel base will be squirelly to handle. This lets you dummy up the wheelbase and the height at which you want things to be, and the amount of frame kick-up you want over the rear axle.. If you use a 4" dropped I-beam with model A cross spring and stock model a crossmember, the height of the frame at the center of the front axle will be 15 1/2" off the ground (if you are running a small block chev engine and 26" O.D. front tires). There is a lot of layout and calculation involved in creating your own frame from scratch, but people do it every day. Good Luck.