If you want to know what shape the engine is in and have the time....
Pull out all the spark plugs (marking the wires as to where they came from) then with a compression gauge, do a "Dry" compression check by cranking on the engine about three or four turnovers (try to do the same for each cylinder). Write the number down on a piece of paper. Drawing a square and putting four lines on each side to show where the compression was taken at will work.
Then squirt about three shots of motor oil into each cylinder as you take the Compression "Wet". Do all the cylinders (oil just before each test) and write the numbers on the paper just below the "Dry" numbers.
If all the compressions taken "Dry" are within twenty pounds say 130 to 150 PSI, the engine is going to run pretty smooth.
If you have a low compression of say "80" PSI on one cylinder "Dry" and it goes to 120 PSI after the oil, you have bad rings, the oil sealed them for a few moments and allowed the pressure to climb, a total rebuild will be in order. If the compressions don't climb more than a few pounds, then the rings are good and the valves are more than likely shot/burnt and rebuilding the heads may be required. You can even go further and put air to the cylinder that has low pressure and at top dead center (TDC) on the compression stoke, the bad valve will either be hissing out the carb (or intake) or exhaust pipe, but at that point it is kinda mute, but at least you will know what is going on.
On the older V-8's, the timing gear tended to "Jump" gears around 80,000 miles or more, the newer ones starting in about the early 90's didn't seem to have that problem. Most of the late 90's up to now can go 200,000 miles with little effort as long at the oil is changed regularly and air filter is kept clean.
If all the cylinders are pretty close in the compression range, but the engine runs rough, you may need new spark plugs, spark plugs wires, rotor and distributor cap. There may be other issues, but I figure that this will put you to sleep pretty quickly....