Strange Ticking Noise is coming from my transmission?

I have a 1973 Dodge Dart Sport it has a 318 with a 904 Automatic Transmission. When the car is idling it has a nasty tick to it. sometimes its loud and noticable others its very light or not even there. its 100% coming from the bell housing so is there a bolt or something that goes in there that could be too long or what?
Also the engine itself is 1968 could the flywheels be different from the old 73 engine the torque converter and tranny is a 1973