Under sized carb for initial start up/break in.

For engine break in, just run it and figure out quickly if it’s too darn lean. If it’s rich, it won’t matter much. To lean causes to much heat.

Put a timing light in it ASAP and just set it so it’ll run on its own and not to advanced or retarded for the break in. If no timing light is available, twist the distributor to advance it until the engine doesn’t pick up anymore rpm and then twist it back to back down the timing and relieve it some.

You should have a vacuum gauge. When the vacuum reaches the highest point, leave it there.

That’s what AJ is saying.

Everything else above that AJ was saying is good info but not needed for engine break in.

After break in, carb tuning takes a little time and you can work through it easy enough. Sometimes, the carb is good OOTB with maybe just a jetting change at most. Super dialing it in is your call. Drive it and make the call. When you’re happy with it, you can stop or push it. Again, your call.