Welcome to the site! I would check to make sure your mechanical distributor advance is working. You could buy a timing tape for the balancer if you don't have and advance style timing light. The other thing I would do is to make sure the secondaries on your carb are opening. You can check the lower plates mechanically and then play with the spring tension on the vacuum operated plates. It's been a long time since I've done this, so perhaps someone else can chime in too.
