Terry,
I could write a book on all of the possible reasons for your trouble so I'll touch on the more common causes.
Elevation change on older cars can be tricky; you may have been running rich as you gained altitude thanks to the thinner air. You can make adjustments to the Idle Mixture Screw, possibly netting some moderate results but what you really needed was to change the jets; not all that convenient.
Fuel delivery is another possibility. A weak Fuel Pump, clogged Filter(s) or an incorrectly adjusted Float may have left the Fuel Bowl low, starving the engine for fuel, and in some cases, if the incline is extreme, the fuel in the bowl could overflow. Did you notice any black smoke trailing you as you were climbing the mountain? You did mention carbon on the plugs.
Engine temperature is another area to look at. If the engine gets too hot it will cause the fuel to burn more rapidly during the combustion cycle. If full combustion takes place before the piston reaches TDC, the result is a knocking sound; sometimes referred to as pinging. You get the same knocking if the timing advance is too great or if you use low octane fuel. Lower octane fuels burn more rapidly than higher octane.
Check the water level in the radiator. Insufficient water and anti-freeze will also cause higher engine temperatures, again resulting in a premature combustion cycle.
Make sure that the Diaphragm in the Distributors Vacuum Advance is supple. If the diaphragm has hardened or developed a small hole, the timing while driving will be off; something you may not notice at idle when checking the timing. Make sure that the Distributor is secure and check the inside of the Cap for Carbon Tracking.
The plugs could also be at fault. If they overheated during your trip, the insulators may be glazed or cracked or if the ground electrodes have eroded, they could fire prematurely. Incorrect or poor quality plugs can also be the problem.
If there is any carbon build-up in the cylinders, there may be some hot spots that can cause premature ignition. See if your local auto supplier has anything you can spray into the Carburetor or add to the fuel that will help blow the carbon free. I could tell you to use plain water to blow carbon free but unless you are experienced at spritzing water through the Carburetor, I would not attempt that method.
Make sure that all of the Carburetor Linkage moves freely. At full throttle, the linkage sometimes bends.
If for some reason the fuel that is metering through the Carburetor is being restricted, you may be running lean. Lean = Higher Engine Temperature = Rapid Combustion Cycle = Knocking.
It could be that all you need is a tune-up and it wouldn't hurt to disassemble the Carburetor to make sure that all is clean and that no gasket damage has occurred. Inspect all of the parts for damage, ruptures, etc. Check the Air Filter and change the Oil; make sure that the Oil is not Milky looking.
Hopefully, something above will fix the problem. If not, send a note; there's more stuff that can be checked.
Take care.
Ray
