I asked the seller and here is the response:
hello case12, thanks this is an awesome car.Unfortunatly I do not have a Marti report or a original bill of sale.I bought this car two years ago as a gt/cs as far as I'm concerned it is.If you want something truely authentic this is not the car for you as it does not have the correct steering wheel,paint job,wheels,pony logo on the grill, or even engine for that matter. This is a restored/modified custom 68 gt/cs.
I would agree with the seller that this is a custom car - which I really like - the custom part appeals to me. But I would want to know if it is a real GT/CS. I guess someone would need to do a fast turnaround Marti report to find out. Casey