Need advice on a '71 Z 4-speed tranny

[blueovalz]

I was helping a friend stab his 4 speed tranny yesterday when I noticed the tube that the throw-out bearing slides in and out on was loose and wobbly. I told him I didn't like it and we proceeded to take the bellhousing off to investigate the problem. With the bellhousing removed, it appears the front input shaft bearing has a thin round metal ring (like a shim) that loosely fits between the bearing and the back side of this tube (the tube is in the belhousing) in question. It also appears that if another shim was added to this, then the tube would be pushed forward against the tube's front stop, and thus rigidly secure the tube in place. As it stands now, the small gap (about .020") between this bearing/shim combination and the backside of the tube is allowing the tube to become loose in a fore and aft movement that then allows it to rock side to side slightly as well. I inspected the snap-ring around the front bearing to make sure the bearing had not been pushed rearward, but the snap-ring and the bearing appeared to be in their correct locations. One last thing. If the bellhousing gasket is removed, it would allow nearly all of this gap to be eliminated. I must assume though that this gasket is a requirement. Any comments or suggestions for those in the know? He stated the tranny worked fine when he pulled the engine/tranny combo.