Another CV joint question.
 

I took my car out for a spin Saturday night and noticed an audible noise coming from the rear of the car while the clutch was engaged.

It was a click or clunking noise that seemed to increase with speed but only while the clutch was engaged.

The car performed as normal and I drove it home. I have not got it up in the air to inspect yet.

I am hoping it is simply C.V. joints failing.

I did park the car and with the transmission in gear, I tried to roll the tire back in forth by hand. I noticed some noise and more play than I expected.

I have been hammering on the poor old thing a fair amount lately so I am not too surprised that something failed but the car has seemed bullet proof for years.

The car is equipped with a non S gear box from a '74 with the 4 bolt flange with the pin rather than the 6 bolt flange that the s gear box had. I also have about 100 extra horse power in the car than a stock '74.

Can anyone confirm that the CV is probably the culprit or should I look further $$$ into the gear box?

Hard to tell without a visual inspection.
If the CV's have a lot of time on them, it's time to redo them anyway.
Noise can also come from the bolts working loose.