What Ford mustang from the 90s - 2005 is the fastest and cheap to buy?

I'm just checking prices to fix a 67 mustang but I need to sit a different engine but I want to buy a fast cheap mustang to take it apart and put the engine and transmission on my 67 mustang.
Now I'm not really good at cars and don't know much of Ford cars, I'm more a Chevy person like I know little bit of Chevy engines.

Bought a used manual ford mustang 2014, huge reversing problem. Transmission?

I bought the car for around $15k. It seemed pretty good, but i noticed the reversing problem after purchase. So when i put it into reverse and turn the wheel fully to the right or left, it seems like my car is hitting something and my car is driving over a huge rock. And then after reversing and putting it into first gear, it also seems to run over a rock but much smaller. What the hell is thr problem? Is it the transmission? Axle? Tires too big? Am i putting too much clutch? I brought it to the place i bought and they said its something all manual cars do. Need to know what's happening. I have around a 20 days for the lemon law. Let me know please.

My Mustang's battery light came on then went off after a second or two?

I was driving my 1999 Ford Mustang GT yesterday, and twice the red battery light came on for a couple seconds then went off. My car continued to run normally when this happened. I took it today to my trusted mechanic, and he did a voltage test while the car was on, as well as the lights and AC, and it showed about 13.8 V, towards the bottom end of the range it should be. The last three times I've driven my car I didn't see the battery light come on again. My mechanic said my car is fine but that the alternator may go bad in a couple months or so, and that the light may have been a warning as such. In February I had the battery replaced so it is still pretty new. I just want to make sure my car will be safe to drive for at least the next few weeks. I do have to drive about 50 miles to and from a business conference this weekend and I want to make sure there's no real chance it will stall on the freeway.

Added (1). I had the alternator replaced about 7 yrs and about 44,000 miles ago, if that helps.