Timing for start up

Yep. Find TDC, then line up the marks and then put the damper at 10 degrees advanced and then line up the rotor in the distributor with the #1 terminal lined up with the rotor at 10° advanced. Fire it up and then make adustments.

If it backfires out the exhaust, it's too far advanced...

to advance the timming are you pushing the vac advance towards the back of the car, or pulling it towards the front on bigblock?