I just thought that I would way in on this. I am at the track every weekend keep in mind that I am at 3000ft altitude. Average time for the LS1's 13.8-14.1, New GT's 14.4-15.0.
I run a 14.7 and I have beat a bunch of the 4.6L but I have never beaten an LS1 unless you count the two that broke down at the line
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88 mustang gt convertible bored to 306 BBk equal length headers, mac cold air fender kit, 3.73 FMS gears, Steeds Tri-ax shifter, Steeda underdrive pullies, Custom off road X-pipe, 2 chamber flow masters, cowl hood, nitto drag radials, ford racing clutch, 160* thermostat 16 degrees of timing electric fan off 94' t-bird jacobs electronics cap and wires. Edelbrock 1 1/2 inch drop springs. (Best E.T. 14.79@93mph @3000ft)