I see an issue right off.. The weather seal on the cab over window has failed. That will allow water to infiltrate under driving pressure.
I'd do a very close inspection of the cab over area for water intrusion by lifting up the cushions and looking in the front corners for signs of mildew (black marks at the seam between the shelf bottom and the vertical wall) for starters.
I'd also have a pressure test done (blower door test). Any CW can do it for a couple hundred bucks and well worth it. I bet tat that age, it's a leaker.
CL sellers always ask pie in the sky prices. Price is negotiable depending on how bad the water has infiltrated. Resto is very, very expensive.