904 causing knocking noise?

Ok, you gave me a hint right there; the engine seemed to get stuck.
-A long time ago I had a 318Dart904. It was eating the thrust bearing. I could hear the tell tale clunk sound. Circumstances prevented me from fixing it. Eventually the convertor/flexplate assy was able to move far enough forward that the bolts could snag on the back of the block. Like you, I hit the key a couple of times and away it went. When I finally got to it, the bolts had chewed part way through the rear cam plug as well as "grooving" the block.Of course the crank thrust surface, and the bearing face,were toast.
I have a hunch this may be your problem too. Now go check that endplay.See post5

-As to the ticking;I suspect its related to that endplay as well. It could be that when the crank moves to the rear it smacks the thrust bearing on the front, and then when it moves to the front it drags the convertor bolts into the back of the block. So you get the clunk and the tap; randomly at idle, in neutral, due to the nature of the firing pulses.
-When you put it in gear, the TC and pump put a load on the crank, and if the thrust was towards the rear, everything would be quiet.
-Then again, the bolts could just be loose, as others have said.Doesnt speak to the clunk tho.
-So get under it already,lol