Jeff,
If it were a new or newer car, then yes, avoid salvage title without a doubt IF you can at all costs.
On a 1975 Corvette, even IF the title became branded as salvage, here is how to lessen or eliminate the potential financial impact of it. ( although I suspect that it will not be branded as such, as it is common for collector insurers not to brand titles of
cars that old. Have seen that a number of times, but no matter)
1- take complete pictures of the car, both before and after the damage. We all have before pictures.
2- save both estimates, the shop and the insurance company.
3- save the documents explaining what the insurer proposes.
4- photocopy all, scan all so that you have it everywhere.
5 agree to the offer. I interpret that they are paying the agreed value of $25,000 less the salvage of $10,000, resulting in $15,000.00 to you and the title
6- repair the car at your chosen shop.
7- enjoy the car.
Almost every old Corvette has had damage, some extreme or significant restoration work performed on it. Said work enhances the value. Your documents and pictures confirm a minor mishap, now corrected.
A mostly original low mile 75 like yours will not be affected much or at all by going that route.
I recall you have a documented low mile car, that added new bumpers, which is very common. The small damage even if with branded title, would only be an issue with a near moron on a car of that vintage.
I am guessing the damage involves the headlight surround and or the fender, again almost always found on an old car.
Relax, and yes WITHOUT A DOUBT, SWITCH TO NCM once all is completed, saving your file in case you need it to value the car at 25-35.
Good luck and keep us posted.
Marty