Another test you can do is a vacuum test. You want to use an undamped 'diagnostic' type vacuum gauge. Use the info here
to interpret the readings.
On a stock engine, often setting up the distributor's mechanical advance can help, along w/adding some initial timing. This can depend on how much compression the engine has, along w/the quality of the gas you're using. The idea is to give the engine as much timing as it can use, w/o causing it to detonate. More on that here
. You'll notice the page was originally on the GM HEI (which could be a good swap for you to make), but the timing advance info still applies.