Easy to see if timing is the issue, simply try it with the coil wire grounded. I agree with Memike that the coil may be getting hot and failing. You still run breaker points? This could be a symptom of a bad condenser. There should be two. One on the positive terminal of the coil for radio supression. The one in the distributor is the one which would give you trouble.
You said it cranks slow when hot. I'd concentrate on battery/ starter/ cables.
You need to find someone with what is called a "carbon pile" load tester, something like this:
http://www.prestolite.com/images_training/carbon-pile-tester.jpg
These are a great big not to mention huge variable load resistor in series with an ammeter, and with a voltmeter. You can.................
1---Determine if the battery is able to "put out" actual real world current for cranking
2---Determine how much the starter is drawing
3---And, using a voltmeter across the battery connections and cables, determine if the cables are causing too much drop.
4---The other possibility after checking the above is that the engine has developed a bearing problem and is getting ready to seize. Usually, this means it will be down on power, and this doesn't usually last very long.
IF the engine seems to be cranking slowly, the above is almost a necessity, unless you want to just "throw parts" at the problem, IE "guess" whether the battery, starter, cables are on shaky ground. However, if you DO replace the starter, DEFINATELY go to a modern "mini" starter. I hate the sound of them too, but they DO crank faster and draw less current.
With today's fuel, and before I went EFI, the three best things I did for hot starting, fuel wise, is
Installed a thick heat isolator under the carb
Built a vapor return system
Converted to a rear mount electric pump.
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