How are these cars compared to newer cars?

[John Z]

You can do anything you can afford. The key is research and doing things in an orderly manner. You can put a mod motor in, but it require changing the front suspension so that you can remove the shock towers. You can put in a 6 speed, but you will have to reshape the transmission tunnel. You can put in a Jag independent rear suspension, but you need the frame work to support it. The list goes on and on and the dollars pile up. In the end it will probably cost as much as a new car, but you'll have the styling.
Alternatively, you can take a small step "back" in technology and use a 351W, T5, and 9"rear with good gears and traction lock and have a really quick and reliable car at a much lower cost.
Research
Of course even after doing all of that, you will still have a trunk mounted gas tank, no air bags, etc.