New motor backfiring through carb

Lets review the scenario, engine runs, remove from test stand,dyno or whatever.
Install engine in car, bolt on torque convertor or flywheel. I suspect engine was turned during some part of this, likely with distributor out. And likely distributor was out.
If crankshaft was turned over once or any number of times,on odd numbers then distributor could very well be out 180.

I believe somehow it is 180 out. Not sure how but I screwed up somewhere. I also actually never did remove the distributor during installation. I took the cap off when dropping the motor in but it was marked as well.