for 63 Sport Fury: I understand that Firm Feel and Steer and Gear achieve tighter feel by using stronger than stock springs. Are there any other parts that are needed to convert to a firmer feel? Firm Feel won't sell me the upgraded springs, and I read an old thread here that indicated that Steer n Gear won't either. Anyone know the specs? If so, i migh ttry to source stiffer springs on my own. thanks!