I need some advise on a clutch, my stock one is starting to slip. I tow a 19,000# trailer and have the mods listed in sig. with the NV5600 trans. I set the TST to level 4/2. I was thinking of southbend, but not sure which one I need. I don't really want something to stiff. Are the aftermarket hydraulics really necessary? Where Can I get the best price? Thanks