My 88 5.0 with shorty headers, offroad xpipe, mac catback with no tailpipes, 70mm throttle body, and 4.10 gears ran a 13.2 in the 1/4 on street tires and a stock engine with 200k miles on it. I put some fully reabuilt cobra gt40 iron heads on and it ran a 12.9 on the same tires and same 200k shortblock. This was with a stock 5 speed tranny aswell.
5.0s are slow as balls with stock gears. Throw some 3.73s or 4.10s in and its a completely different car. A completely bone stock 5 speed 5.0 with 4.10 gears is a high to mid 13 second car depending on the driver
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