New motor backfiring through carb

Why not roll it forward and get a little lead time on the ignition? Make ir easier on yourself. If I am wrong let me know, it's what I plan to do.
You can, once you have 0, and #1 pointing at the correct pole on the cap. If you have timing tape, or marked your balancer, if you want to rotate the motor to say 12 btdc, roll the motor to that mark, move the distributor to line back up on the cap, and lock it down. May not be exact, but will be close. Id still check it with a light