Arlie,
I built a 67 Mustang coupe that was a bit of a GT/CS clone. It had side scoops and a spoiler trunk lid and end caps. This, plus a front air dam and a 69 Mach I hood scoop.
It was powered by a stock 250 6 shooter. The one other add is I removed the 3 speed toploader of the 67/68 era and bolted up a toploader 4 speed! It is a direct bolt in with the same clutch and same driveline. A true bolt in with of course the 4 speed shift linkage. No other changes at all.
The 4 speed woke up the six cylinder a whole bunch! The 3 speed has such a huge gear jump between 2nd and 3rd it really hurts the six. Give it the extra cog of a 4 speed, or better yet a 5 speed, and it is really fun to drive and works quite well. My car had the stock 4 bolt rear end with 3.25 gears that also helped a bunch.
The six has plenty of poop when given the extra gear spacing!!!
Rob
And by the way, there are 4 bolt style steel wheels available! No one will know and that is what I am doing with the current build in my shop for a customer.
http://www.kentuckymustang.com/product_p/7610.htm