Well you are putting a lot of thought in to this for sure, very desirable car I would bet the owner knows that, at this point he has money in the car to paint and putting back together to date beside the long term ownership...he will more than likely want more than its worth...i would try to back into the number based on finished car well done worth 28-30k. The car has glass and interior installed are you sure it was all removed in the repainting? The Heater holes still hanging out of fire wall makes me think the repaint was not all that well done The state of the engine matters a great deal as far as worth...way to many unverifiable items...what really matters in the end is do you feel up to the adventure of finding the missing parts and finishing car....my guess is he will want 14-16k....good luck let us know....Barney