My understanding is that the Firm Feel rebuilds consist of choosing parts that are properly fitted to each other with closer tolerances. I have a FF Stage 3 in the Charger with their Fast Ratio arms. This totals up to 11.7 to 12-1 steering ratio. Very fast and great road feel. They try to push their stage 2 though. Maybe because the #3 is so vastly different from the "Tires on ice" feeling of stock Mopar power steering.
If you just want a leak free steering chuck with a steering feel greater than stock, you could also get a Saginaw PS pump and shim the valve. Many here have written about the procedure including Rick Ehrenberg from Mopar Action magazine. It involves adding more washers inside the PS pump to lower the amount of boost from the pump. Some pumps have no washers, some had 1 some had 2. The consensus I recall was a total thickness of around .125 to get the pressure down to an acceptable range. I did this to a pump used in a 72 Duster. I may have to add more shims/washers though. It still feels a bit overboosted.