It's really up to you to find a reputable repair facility to do the
work. Many will offer a warranty of varying degrees. Modern cars are
often repaired by companies affiliated with the insurance company.
Many insurance companies will give you a lifetime guarantee on the
work performed if you use their recommended facility. If you choose
not to, you are on your own.

With antique cars, it's very difficult to even locate a shop willing
to do the work. Most who do are independant restoration shops and
quality and warranties vary widely. It's incumbant upon you to locate
someone who will do a quality job and to hold the insurance company's
feet to the fire if they balk at the cost, etc.

I highly recommend having your antique/collector car accurately
appraised by a professional every 3 - 5 years. It is much harder for
the insurance company to deny your claim or attempt to total your
vehicle for relatively minor damage if you can prove the true value.

As far as your own personal insurance goes, check with insurance
companies thatspecialize in insuring antique autos. Hagarty and J.C.
Taylor come to mind. Hagarty will even pay YOU to make the repairs if
you restored the vehicle yourself. They also pay up to the limits of
the policy if that's what it takes to fix your car even if it would be
considered a total loss.

As an example from personal experience:

My 1956 Cadillac was rear ended in my driveway by a UPS truck. UPS's
insurance company sent me to their preferred repair facility. I tried
to warn them on the phone that they would be unable and/or unwilling
to do the work. They said to take it anyway. Of course the people at
the shop stood around with their mouths agape trying to figure out why
I was sent to them and what they were going to do.

Long story short, they sent an adjuster to look at it who actually
knew something about antique cars. He located good quality used parts
and I contacted a restoration shop that I had used in the past.
Together, they came up with a figure that satisfied everyone. My car
was repaired - better than it was before the accident - and I even had
some money left over.

I hope this helps you.

Forrest