Sounds like what happened to me.
First problem I had when I dropped the distributor in I was off a tooth. When the oil tang lined up it pushed the rotor off #1 a little. It would backfire.
Had to use a long common screwdriver to move the oil pump, and then finally got it to drop in with rotor at #1. Pointer on ball, #1 TDC.
A second problem I had was the drive gear was loose on the distributor. Playing havoc with the timing. That’s why I purchased the replacement distributor.
I only offer my experience as something to look at. You must be frustrated.
Good Luck
