You should have no prob running 12s with that combo at that weight. I ran 10.91 @ 120.56 in my 3100 lb. Duster with "bone stock" 906s & a XE284H cam, PTC 9.5" 4400 stall, 4.10 gears, 9.73 compression, shifted at 5600, It ran 11.12 with a PTC 11" 2800 stall, 1.57 60ft.
Heck i ran 12.5s @ 105 in my 71 Swinger with a junkyard 360 magnum shifting at 5K.
75 Duster, 451 10.87 @ 123.58 NA
97 Z28 6sp., 12.01 @ 115 on a 100 shot
71 Swinger. 360 magnum. 12.58 @ 105
78 cutlass, 469 BBC. 12.70 @ 108 on street tires.
http://www.youtube.com/watch?v=Z2kqNmMfheU
