Is this what driveline vibration feels/sounds like?

[Livio <livio@domain.elided>]

What I love about my new 73 Berlina is that I'm
being forced to learn new things every day!
This car ran so smooth on the highway until
the other day.  Just driving along at 70 mph
and then there was a sudden vibration so
I immediately pulled off and drove along slower
roads.  Now, when I go above 60 mph a droning
sound builds in volume.  It is difficult to tell where
it is coming from, but it feels more like the back
then the front.  The stick shift has a vibration to
it, and if I slightly push the clutch down it is also
vibrating madly.  The car overall however doesn't
vibrate to badly.  I waited until I mounted new tires
tonight to see if that was a contributor, but no difference.
I looked at the guibo, it looks solid, no cracks.  However,
every second section, the one with the head of the
bolt facing the engine, has a mangled bit.  It looks like
it would have collided with the aluminum housing of
the transmission where the mount is located.  There are
chunks of aluminum missing in the housing. But I don't
know if these are scars from a previous life with P.O.
If I need to replace the guibo I want to understand how
it could have come into contact with the housing,
perhaps I need to change the tranny mount first?
Thanks in advance.

Livio Passera
Toronto, Canada
77 Spider
73 Berlina
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