There's not enough photos of the Shelby to make a truly-good guesstimate with, but just glancing under the hood, it's not a fresh restoration, nor is it anything close to concours-correct or concours standards. And if the miles are truly that low, why was the engine compartment (poorly) refinished? What happened to the windshield washer nozzles?
I get weird/paranoid when I see easy details or components done poorly or not at all, because it triggers the where there's smoke there's fire sense in me.
Anyhow, let's say the Shelby is a good, solid, original-panels and good-integrity car. It's still just a driver from what I can see. If I was paying $89K in today's market, I'd be expecting a concours-ready high-quality restoration that is ready to go for MCA concours-driven or AACA Nationals. I think that's a reasonable expectation for that kind of money. The only 69-70 GT350's that tickle the 6-figure realm are the cars that are at the top-end of that class, dripping in NOS parts and superb craftmanship and every detail uber-correct.
For a very-clean, sharp and good-integrity driver GT350, I would think that $55K-$65K would be tops for me.