The Hot Rodders are the best scratch building resource I have locally. Simple theory, build the car around the wheels. Get the suspension loaded to ride height. We use a stick or rod drilled at both ends the length of a shock in the middle of travel. You might want a set of cut springs for setting it up or load it to settle. Then get the drivetrain in place with the carb flange level(you don't have? help Pat) so your motor with the
oil pan you're going to use (low profile?) has it's butt level with the frame bottom. Then try hanging a body over the whole thing or mocking it up for stance, ride height and "attitude" of the car.