[Verdoro 68]

A compression test and a leak down test will give a sense on the overall health of the engine.

White smoke would indicate coolant is making it's way into the combustion chamber. You'd also likely smell it in the exhaust. A bad freeze plug wouldn't allow coolant in the combustion chamber, but would cause an external leak. Usually a bad head gasket is the cause of coolant in the combustion chamber. What do your spark plugs look like?

There are two different water pump lengths in '69. Unless you have a mismatch in pulleys and they're not aligned, the water pump length wouldn't cause a squealing belt. Make sure you have the correct width belts and tension on them. There are a bunch of threads in the street section on belt sizes. I have a diagram somewhere that shows the correct width per application.

What are the shifting issues with the transmission? What's the trans fluid look and smell like?

For the sounds, I'd put it on a rack or some ramps while it's running to trace the source.