Aod Clicking Sound

On the engine side of the torque converter the is a drain plug that protrudes thru the flex plate. So there is a hole in the flex plate for this and if its not aligned to that hole (IE 90 or 180 degrees off) it will push a portion of the flexplate forward and possibly rub against something (or too far on starter gear). Easy to check and see with inspection cover removed and rotating engine. I made this mistake on my cousins car but found it quickly. I'd check that first. Also make sure you have the correct starter for that flexplate.