As it sits, it's a modified turbo - and a 3.0 at that. Miles are too low for a driver.
Does it still have the chocolate brakes? What about the original valence, seats, wheels, tail? Exhaut? Motor looks kind of stock. Who fitted the strakes? Should'nt a '75 have the early (NLA, hard to find) tall headlight washers?
Guys who want a modified turbo likely prefer a 3.3 (certainly would prefer the brakes), probably prefer to tune it themselves, likely don't care enough about "low production #" to pay for it, know that upgrades have a very tiny return (or even detract) on resale. Worse, they probably want to drive the car, so very low miles isn't great for them. And they're a very small market.
Folks who would pay for "#47 of 50" probably prize non-restored originality above everything - and prefer to see the owners handbook/service book and a useless 30 year old spare fan belt in a time-capsule stock car with no non-factory parts or changes at all. Not even powder-coating on pulleys, much less an aftermarket intercooler in a year the factory didn't use one at all...
That's where "investment" money goes. You should pitch at the second group, because they'll pay twice as much as the other guys. You can probably get all the parts you need to return to stock from the first group, though
My $0.02