Timing Vortec

[1966chevyc20]

Alright I have an L31 vortec crate engine installed in my '66 C20. I'm running a summit HEI distributor and having trouble getting it timed correctly. From what I understand I should have 10-12 initial timing with the vacuum unhooked and plugged. And somewhere in the 32-36 range total timing. I am having to use a advance timing light and when I try to retard the timing to line up the marks it dies. To get the marks to line up it is at a ridiculously advanced initial timing. Any ideas as to what could be going wrong here?? It also backfires through the exhaust when I speed it up.
Questions:
1. Is it possible to have the distributor off a tooth and still run?
2. Is total timing with or without vacuum advance hooked up?
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