[villagetinker]

On the flip side, many of the systems in the older cars are MUCH simpler then the new cars. I have totally rebuilt 7 Mustangs (64 to 69), and all of these ran very well for many years, until I sold them. I kept the '66 fastback, hope to be showing it very soon.

OP, as pointed out above, I generally agree with the above comments. I actually replaced the entire wiring harness in the '66 Mustang due to concerns about wiring. I actually had a fire in the '64 1/2 convertible when the generator regulator failed. Fortunately I was able to disconnect the battery and use a fire extinguisher on the burning wires.
There are lots of things to be checked, but some items that would be on the top of my list:
Fuel system, gas tank inside rust, rubber lines (these do not like ethanol in current fuels), carburetor seals and fuel pump (all due to ethanol in fuel).
If you will not be abusing the engine, the valve seats will probably be OK with unleaded fuel, but if you intend on hard driving hard or long distances, you should have hardened valve seats installed.
Brake fluid should be replaced, DO NOT USE THE NEW SILICONE BASED brake fluid unless the brake system was rebuilt for the new fluid. The brake cylinders need to be inspected for dirt and moisture. My '69 had some much corrosion and debris in the wheel cylinders they froze up.
All other fluids need to be checked and IMHO, replaced with fresh so you know when to change and you can monitor for leaks.
All filters need to be checked and probably changed.
All lights need to be checked and replaced as necessary. There are Halogen replacements for the original headlights available.
Hope this helps.
PS, I still stick with my original comment above.