Thanks guys, it's sorted. the clue was a second score mark on the prop shaft. I dropped the shaft again and this time noticed the long self tapping screw protruding into the tunnel. A previous owner had used one to locate the front of the hand brake bracket before rivetting! The new gearbox mounts (standard gearbox)must have held the rear of the box and propshaft a bit higher hence the more frequent squeal.

The lower frequency rumble was a bit more bizarre and down to me. Rust on the faces of the rear UJ stopped it fully engaging with the diff flange and left it very slightly off centre and about 1mm forward. It became obvious when I slackened the bolts and found one stiff in the bolt holes.

Thanks again

Pull the handbrake a bit and see if the squeaking is gone.
Check the rear lever where the cables are deflected

Can I suggest that the problem may further back/front , it may be worth checking the rear springs, may tired or broken leaf,worn bushes, or broken pins/shackles also the soft front engine mounts all would alter the drive train alignment, finally I assume you have a 4 speed standard gearbox
Trevor

The car emits a metal to metal type squeal on some road irregularites also on engaging clutch with engine revs as in a vigourous hill start. It doesn't appear to be suspension telated and the only indication I have found is a bright scrape ring on the propshaft where it has contacted the front propshaft tunnel arch. Static separation is around 1cm.

I diagnosed soft gearbox mountings allowing the tail of the gearbox to move and have replaced them. The UJs were in good condition. The new rubbers appeared rather thinner than the originals but then the originals may have swollen with oil.

On road test I found the noise to be more frequent and has been joined by a lower frequency rumble under load.

Any suggestions on what next much appreciated.