[ThreeQuarter]

I bought a ready-to-run 327 from a individual. A few years later I have it in my pickup and it's running, but it's not running as well as I expected. It will idle smooth-ish, but with an irregular, subtle hiccup. The engine also lacks the power I expected it to have.

The engine is supposed to be built close to the specs for a 300hp 1963 Corvette 327. Here's is the other info I was given:
1. roughly 10:1 compression ratio
2. comp cam 12-234-2
3. 76cc open chamber heads'
4. Pertronix ignitor 1 and flamethrower 1.5 ohm coil

Here's what I've observed when I try to tune this engine:
1. The engine requires a ridiculous amount of advanced timing--in the neighborhood of 40deg while idling without vac advance.
2. If I try to back timing to where I think it should be, the motor bogs and dies around 10deg BTC.
3. I'm getting decent vacuum of about 16.5 when warm and idling at 750rpm.
4. The 6" factory-style balancer is not spun. The keyway and the timing mark align perfectly as I understand a 327 should.
5. The timing sprocket dots are aligned, and the crank sprocket is using the neutral/factory (circle mark) keyway. Chain is new and tight.
6. I have swapped out the intake for a different one, and discovered there was probably a vacuum leak there, but I think I have solved that with a new intake and better installation.
7. Pertronix says their system either works or it doesn't work at all, so since it works at an odd timing, they are directing me to other areas.
8. I found the breaker plate ground wire was loose where it grounds to the vac advance assembly, but after cleaning and tightening that connection nothing changed.
9. I'm running 91 octane fuel currently.

What could cause this?
1. Any other easy things I can check?
2. My carb is too big for the motor (Holley 700cfm), working on changing this but haven't yet. Could that cause this in any way?
3. I haven't clocked the cam, is it possible I have a different cam than I was told?