I ran S/S springs on my 68 Dart for years , it actually ran its best e.t. at 10.40 and best 60 ft 1.40 ( foot braking ) with them . When I went to Cal Tracs and mono leafs my 60 fts were not quite as good but they were more consistent . Currently I run on a throttle stop to run 11.50 : 60 fts are 1.48-1.52 depending on the track. Car is 3150 lbs with me in it , 410 inch small block, 904 , 4900 stall 8 inch converter , 4.30 rear , runs 10.80s off the stop