There is a vid on streetfire of a guy with just H-pipe and slicks doing 12.6. Another of a guy with just slicks doing 12.9.
You can do it on street tires with just exhaust, and gears. Dont even have to touch the engine(may not even need the exhaust, just gears). It all depends on the driver.
It shouldn't take much to get a Mach into the 12s, depending on where you live. Here's a video of a Mach running 12.54 with just a Prochamber, K&N Filter, and 275 Nitto Drag Radials:
I actually had the opportunity to line up with a stock 2003 Cobra about two weeks ago. I know these guys at a car lot and convinced them to bring out the Cobra and line up against me. I was really surprised at the outcome of the race. From a dig, I took him out of the hole by about a car length or so and I only wrapped it til the end of third gear, and the Cobra had only caught up to the back of my door. From a 20 roll, we were even through 1st and 2nd. 3rd gear he started to slowly pull, but not by much. We let off at the beginning of 4th and he wasn't even a full car length ahead of me. I could tell the guy couldn't drive it too well, but either way, I was surprised that I didn't just get it handed to me by at least 3 cars.... I'm certain he would have seriously put the lengths on in 4th gear, but we didn't have much road to work with, so it turned out to be good for me.
yeah the 03-4's have a weight and a problem called IRS LOL they are only about 1/2 sec stop ahead from the mach if both have slicks. damn near a driver race if the cobra is on streets and the mach is on slicks.