I have a SBC 3600 DD and i love my clutch. I pull a goose neck that wieghs around 6000 lbs with a pull truck that wieghs 6200, it is smooth on apply doesn't jerk and doesn't shift hard. the guys at sbc recomends the dd if u pull a trailor very often. I know a few guys with the single disks and they do not hold up very well unless u go with a big pressure plate pressure which that affects the shifting and driveablity.
2000 F-350 srw, ex-cab, lwb
TS 6 posi-chip, ATS compressor housing, AFE stage 2 intake, DD SBC, boost annihilator, 3 1/2 down pipe, 4 inch exh, BD waste gate
1975 F-150 4wd 6200 super stock pull truck
built 462 ci motor with eliminator block, billet crank and rods, scj heads