I have the firm feel #2 box, and just yesterday put on the Fast Ratio idler and pitman arms. Its better than stock, still not like a modern sportscar. I would not hesitate now, to go to a #3 Firm Feel box.
FWIW, the Fast Ratio idler arm (optional according to FF) just barely clears the exhaust tube ( I have 2.5 TTI tubes, and factory HP manifolds) im talking Millimeters. Its because of the Grease nipple though. If a recessed nipple is used then you get all that nipple clearance back.
A taller seat just cramps your legs against the steering wheel more. (ask anyone with a 6 way seat)