Well, a 6.4 needs mods obviously, so allowing mods on a car is more than fair. A 03/04 cobra with exhaust and a tune will mutilate a 6.4, 0-30,60,90,120 no matter how you slice it. And be more reliable, better mpg, etc. I've seen factory stock 6 speed ws-6's run 12.9 on drag radials, all else stock. Now...saying that every tuned 6.4 is a 12 second truck is false, I've seen several in the 13's. A stock lightning has that beat. I guess when you say 90%, you're talking buicks, oldsmobiles, half ton chevy trucks, old bone stock lt1 f-bodies etc.
Fact is, a 13.3 @108mph 6 speed stock z28, will out run a 12.7@104mph 6.4 on the streets all day long.
I read your post and know exactly what you're saying. What I'm saying, since you can't grasp it, is for something fun , on the streets, daily drivable, etc...you're not going to top a sports car, with a truck. Initial investment, money in mods etc., it's not happening.