Does he have a stick or auto?! Stock for stock... a 2005 V6 mustang is about as fast as a Mark... both of you guys have mods so it is very hard to call this one.
Judging by the fact that you ran a 14.3 I'd say you got the edge.
Race at the track, anything can happen on the street. Slower cars win all the time on the street. I remember my friend had an 88 Mustang GT convertible 5 speed, he had exhaust and and a cold air intake on it, basically stock... he used to beat my 95 LSC on the street every single time before I had gears and trac-loc. His torque would get me off the line every single time and I couldn't catch up before we shut down. At the track he only ran a best of 15.6 at 88mph while my car was in the 14.3-14.4 range before the gears and trac-loc at 98mph. That's a huge difference in performance...