ALL new parts >> STILL CLUTCH CHATTER

Ok... I'm REAL fed up now!! I put a fresh clutch in two months ago, and bought an aftermarket flywheel and adjustable cable & quadrant. My original clutch wasn't slipping, just a real annoying chatter when you back up, downshift, or take off without nursing it. Anyway, ... it improved but still wasn't right. I yanked it all out, opted for Ford Racing clutch AND flywheel this time. Again, better, but still not right.I replaced the tranny mount and u-joints, none of which appeared bad, but , you know... just because. STILL no F-ing improvement. Now it's pretty much only when you back up, maybe justa touch when you downshift. Someone suggested the car had been beat before me. ( Ok, so what used GT isn't ?)... .but to have the input shaft of the tranny checked, as they bend? when beat upon. HELP !!!!! What's next to check??? I don't have $500 to fork over to the boneyard for a used tranny, just to have the same problem. UGGGGHHHH!!!!
Um, thanks for listenin to me whine. HELP!

Chatter

I guess that is where I notice it the most also. Sucks. Must be a common trait with Stangs. Now I have a new dilemma..... I have a Pro 5.0 shifter in there, and as of this past week, when I downshift into 2nd , from 3rd OR 4th, it grinds and pops out. I noticed it again tonight when I was cruisin along in 2nd and let off the gas, it popped out. First I'm gonna throw my old stock shifter back in , see if that solves anything... if not... .might be time for a tranny rebuild. Sucks, coz I baby the car and don't use it that often since I have a company truck.
THANKS for the input!!!!!!!