Whacked alignment

When I bought my Spider in 2008, part of the reason it'd been off the road since
1977 was due to an off-road excursion while verifying a rally course. The car
took damage to the passenger side driving light, headlight bucket, hood hinge,
and the oil pan. Limping it home, it blew a head gasket, which was what
ultimately sidelined the car for 31 years.

It also partially collapsed the right front shock tower.

In 2009 & 2010, I rebuilt (almost) everything, and got the car back on the road.
That was when we discovered the shock tower damage. It wasn't 'too bad', but
the alignment couldn't quite be brought back into spec - the tire still leaned a
bit. I was told I needed to have it fixed (pushed back out) while the engine
was removed.

To tide me over, Giovanni at Autosprint had 'compensated' as best he could, but I still ground off the previous set of 13" tires.

Then, last spring I blew out the used engine I'd installed, so I had the
all-too-rare opportunity to have the shock tower properly fixed. Last fall I
got my engine back & installed, and foolishly, I did not run straight to an
alignment shop when I put on my brand new set of 14" rubber.

6,000 miles later, both front tires are wearing horrifically on the inside
edges. The passenger side is already down to the belts!

However, the local Streamwood Firestone shop says they can do a correct
alignment on my Spider.

Do I trust them? Why have I always heard it's so hard to do on these old cars
'with shims'? What does that mean?

I truly hope they can bring it into spec, but I'm a little skeptical.

Do I trust them? Or do I take it back to Autosprint for Giovanni to fix?