Well, this is a tough position you're in, besides the keep original or modify it route.
The problem is your wife's (and many other people too) expectations of a car with 40 year old technology performing and handling the same as a modern car.
Yes, you can mod one of these cars to the point where they are close to todays cars but with the amount of upgrades needed it is expensive and will permanently alter the car. Most people go half way with these cars to improve them a bit, disc brakes (maybe convert to power too), dual master cylinder on earlier cars, "Shelby drop", export brace and/or monte carlo bar and suspension upgrades are the most popular. These first ones are basically bolt ons and can relatively allow the car to go back to dead stock easily if desired later on. The most extreme ones are the removal of the shock towers to get rid of that weakness in the design of the front suspension/structure of the car and go with a modern coil over. The addition of welded subframe connectors can be done too. While one of these cars could theoretically be brought back to a stock appearance there would be a lot of work required to do it.
Before I would do anything with the car and waste your time and money, and possibly a car, I would find out exactly what she wants the car to be like and decide if you're willing to do that to this car, the costs to do it are OK, and if she will be happy with it in the end.
__________________ 1968 Mustang coupe, Acapulco Blue, 289 2v, C-4, Power Steering.
Hopefully a 1969 convertible or Sportsroof (non Mach or Boss) for next Mustang project 
Trying to find my father's 1973 Mustang Grande he bought brand new. 3F04F126773 last known registration and title was in New Jersey, 1982. | 
