First, let me say how badly I feel for you.
That was a pretty ****ty thing of your buddy to do.
Lemme guess, there's no police report, is there?
That car hit a curb directly on that right back wheel, and it hit it hard.
Along with the frame and body damage, there is very likely differential damage inside and out, possible bent axel(s) and a myriad of yet undiscovered damage.
If you have collector car insurance on this car, use it to get the damage repaired and then have them sue your pals insurance company to recoup their loss.
Yes, you will have to pay the deductible at first , but once your insurance collects from his insurance they are supposed to pay you back your deductible.
Besides, collector car insurance is going to be much more empathetic to your situation and much more willing to go for a repair instead of total.
You have much to consider here. Take your time and don't let his insurance company rush you.
These cars are 25 years old now and genuine parts are hard to come by. A frame swap might be the only answer, depending on damage, however, that could result in a total and a salvage title.
Personally, I would have a shop that specializes in restorations do the repairs, NOT a dealership. Yours is probably the first one of these cars the techs at that dealership have ever seen, much less repaired.
Even if they have looked at and estimated the car you are under NO obligation to have the dealership do any work on your rare and valuable automobile.
Sorry to have gotten lengthy there, but I'm in the body repair business (at a dealership, no less) and would hate to see you get jammed up because of your buddy's lack of respect and consideration.
Just my 2 pennies worth.
Again, so sorry and best of luck to you.