2600 rpm's w/ 4.10's at 70 mph seems a little overly optimistic - unless you've got yourself a 6 speed trans
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I think you'll be ok w/ the 4.10's, but I do think that unless you get yourself some more rubber in the rear, you'll have a tough launch. And, I do think you'll be close to out of gear at te end of your 1/4 runs.
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'90 5.0 LX - heads, intake, cam, fuel delivery, gears, full exhaust, pulleys, ignition, drag springs, front brake upgrade, a/c delete, K&N cone filter charger.......and much more!
1/4 mile: 12.29 @115
60': 1.78