Well, here I go with another problem, again. My 74 has now developed a vibration. Throughout the car at highway speed. It's not in the steering, wheel alignment is good, shocks, brakes, bearings, tires, and balancing etc are all fairly new (less than 1500 miles) I haven't found anything loose, broken, or missing.

Any idea's as to what may be the problem ?

Thanks                                       

  I HAD A VIBRATION LIKE THAT. FOUND THE TRANS MOUNT WAS SPLIT AND COLLAPSING. WENT AWAY AFTER REPLACING THE MOUNT. WHAT A DIFFERENCE.

                                        REID '72 T-TOP

I'd have to agree with Ron & Reid. Sounds like a u-joint related vib. Along with checking the trans mount, check the engine mounts, also. If the driveline is out-o-whack anywhere, it will create a "tight" vib., unlike an out of balance wheel, which is best described as a "heavy" vib.
The frequency of the vib. tells where to look for the source. Most driveline vibs seem to come & go at a certain rpm range, where a wheel/tire vib is heavy at just about all speeds, but more noticeable at a specific speed.
Check all the u-joints, in the driveshaft, and the half-shafts for looseness/side-to-side movement. If you find the u-joints are the source, before removing the shafts, mark the shaft(s) and the yokes for proper alignment on re-installation. Turning the shafts 1/2 turn out of sync when installing will create a vib., also.
Don't overlook the possibility of a worn clutch/flywheel assy., or a harmonic balancer problem.(isn't this fun? )

Aw crap  it just doesn't stop  . At least with you guys providing this information, I should be able to ID the cause with little problem. By the time I'm done, this car should be better than new. But I won't bet on it    

Thanks guys

I have had a vibration from the beginning with my car also.  So far I have changed all of the half shaft u-joints, drive shaft is next.  It has gotten better, so I think all of my u-joints were just bad.  I know my clutch is going and causing some vibration too, but if I had all the money it takes to do this at once, I still wouldn't have the time.  My wife says this is worse than those golf widows you hear about, and she bought me the car!  Anyway, I drive her just about everyday, with the top down!