Eric,
IF the only serious damage and impediment to driving is the damaged rear torsion bar tube
(and other components damaged in the 180 spin and consequent to the tube failure),
then get it ‘fixed’ sufficient to drive the car.
This won’t be ‘earth shattering’ expense.
This won’t be correctly or completely ‘fixed’ either.
(The torsion bar tube rusted from inside due to condensation in the ‘sealed’ cavity.
You are seeing only the rust on the outside. It is probably more serious inside the double panels.)
The spin only stressed the weakend tube to failure.
You will need to spend some time (and money) getting everything else working and safe to drive.
Now you have (at least) a ‘running 911’.
Now assess what you want to do.
The only way the 911 will ever be a ‘great’ car again, will be to ‘start from scratch’.
This is the expensive and time-consuming ‘body-off’ restoration and un-doing the ’88 ‘repair’
... and un-doing whatever you must do to ‘fix’ the current situation.
The good news is that the result will be better than Porsche built it new and it will never rust as it did.
Now is the time to do this.
There are the restoration parts available and the knowledge to ‘make it right’.
There are even some NOS available.
A few decades from now, this probably will not be possible (for mortals to afford).
It appears as a ‘normal’ ’67 911 without ‘S’ trim.
Some were ordered with ‘S’ sway bars and Koni shocks (and a few, Porsche added the vented ‘S’ brakes).
I see alloy lugnuts so it may have (or had) the '67 optional '911S' 4½x15 Fuchs (or later updates).
This may be the ‘S’ suspension you reference.
Please post more pictures of everything.
We can help you better assess the situation.
The biggest decision will revolve around your (and family’s) attachment to your dad’s very special (life-long) 911.
A 911 like this may have VERY special meaning to a grandchild or great-grandchild someday.
Please don’t lose it.
(I wish I had my dad’s Factory delivery ’66 912 sunroof coupe and the ’67 SW Targa I replaced it with.)
If you don’t restore it now, preserve it in a very low humidity environment and secure all the to-be-unavailable restoration parts.
If you get it drivable and expose it to the current (mag chloride) environment, it will quickly disintegrate.
I hope this helps.
Best,
Grady