Scroll through the BAT graph. I'm sure you can find a couple of comps to give you an idea of the market.
https://bringatrailer.com/porsche/930-turbo/
https://bringatrailer.com/listing/1986-porsche-911-turbo-18/
I would peg it between $95-$115k by your description.
Recent comp. 30k miles
https://www.goodingco.com/vehicle/1988-porsche-930-2/