Actually spoke with the mechanic tonight (he turned up at a classic meet we went to, remembered the car and spoke to me). So I told him what you said, and he said you can't do it like that because it would cock up the camber angles.
He remembered the car, but is he familiar with the design of the front suspension?
NONE of the control arm (upper or lower) rubber mounted bushings are alignment adjustment points.
The caster and camber is adjusted by loosening the upper control arm SHAFT to FRAME mounting BOLTS.
You would NOT touch those.
The upper shaft bushings are retained by NUTS on each end of the shaft. Loosen those.
The inner lower control arm bushing is NOT an adjustment point either.
Safe to loosen and re-tighten that bolt.
Yes, it's likely things will shift slightly
if you do this loosen/tighten procedure as I have outlined.
You should have the alignment checked and adjusted as needed after this, but it shouldn't be very far out.
The bad part.....
If the bushings were tightened with the car jacked up and the suspension at full droop, it WILL cause the bushings to fail early.
It puts a great deal of strain on those bushings to have them "holding the car up" like that.
As you have noticed, the front sits high, BECAUSE the bushings were tightened with the suspension "hanging".
You don't have to believe me.
I'm only 61 years old and have been a licensed mechanic almost my whole life.
I am also very familiar with these cars, having owned and been involved with restoration of several of them.
I suggest you get a repair manual specific to your model and year.
Especially read the chapter on front suspension.
There are reprints of the factory shop manual available.
A Google search will find them.