The only mods are to the top end and the exhaust. Its basically a 351w long block and since parts store didn't sell the rest of the motor's stock parts, I just got what they did sell. Holley650, performer rpm intake, summit headers. And the only pulleys I saw when I was looking was a set of underdrive pulleys. I lucked out and the shop I had rebuild my
tranny had a shift kit laying around, so they threw it in there for pretty cheap.
As far as what your question about what you would run, I just put the following into a drag simulator... 66 mustang, 271hp engine 397ft-lb torque, stock C4, 2.51 rear end, street tires, aggressive driving, typical track conditions. It says you will run low-mid 13's. There are a whole bunch of other numbers that I just used generic answers for. Now it's just a simulator, but it gives you an idea.
Post your 1/4 mile times and what Mods 
If i was running about 225 hp on a 1966 mustang with a c4 and stock differetial do guys think i would even be in the 15's or 16's? Did you do lots of modifications to that 351 to get that time?
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