Issues with a rebuilt 360

With the MSD distributor, change the bushing to the biggest one, and use one light, and one medium spring.
That will get you in the ball park.

Then set the total timing(at whatever rpm it takes for the timing to be maxed out) at 36*.
After you have the distributor tightened down, rev the motor up pretty high and make sure what you think is the total, is really the total.

The initial should end up close to 20* like that.