""their response was between 8and 12.""

That seems like an in-D vacuum reading at around 900-950rpms or so.

Don't worry about the "too much advance" theory for now. Members like me will tell you to throw as much initial at it that you can until the starter gives you fits. Once you know how much it will take, then we can help you with the rest of the distributor setup. I would suggest that what ever initial that you currently have, bump it up my 5 and reset your N rpms and take another vacuum reading. Then bump it again and reset your N rpms, then take another vacuum reading. This test will give you some options. As long as the vacuum increases and your starter can spin it at startup, then it will be fine.

Reference: I ran 18 initial on my 340 with the stock starter and 24 with a mini starter.