454 tbi timing

Good morning. Probably not such a daunting task to some but I am having a tough time getting this right. I changed the timing gears and chain. They are set looking at one another (cam mark down and crank mark up). I dropped the distributor in place with rotor pointing at #1 plug. Only rolling over and backfire. If I take that same set up and put my finger in #1 hole and roll the engine over until it pushes my finger out and co tinue rolling until the piston is on top (TDC compression stroke?), the engine will crank but my timing gears are 180 out. What am I not seeing in all of this?

and then do you have a connector to disconnect while setting static timing so the computer will work correctly????? what year/vehicle is this engine in and what ECM does it have??????