Stock 4cyl 0.702″ 463.6 lb/in 14.00″ 1390.8 lbF

Stock 6cyl 0.740″ 521.8 lb/in 14.625″ 1891.5 lbF

Stock 8cyl 0.765″ 606.0 lb/in 14.7″ 2242.2 lbF

From that site. It does not say if ex cab and regular cabs got any different springs just based on cylinders and nothing special for the R/T, from reading the rest of the stuff it seems they are just talking about the early daks through 96.