I would think around 20k. Problem is going to be finding the parts to make it correct. Guys have been buying up gt350H parts for the last 2 decades and packing them away for when they need them. It will be nearly impossible to put back together.
No such thing as a 1965 GT350H. They were only made in 1966.
Get a solid confirmation of the VIN. If the car is one of the 500 GT350s made in 1965, its like gold. If its a 1966 GT350H, that's pretty cool too. But get up close and personal with the seller first and get the VIN.