That might be one of the best ebay ads for a vintage Mustang I've ever seen. That maintenance book and all the details inspire confidence if I was a buyer. What I don't know is the amount of repair this car has had since new. Prior rust, prior damage, etc. Not a deal breaker if done properly, but original sheet metal cars are hard to beat in value and enjoyment.
I like this car and the presentation very much. I will tell you this, I sold my '65 fastback (GT350 clone) so I could buy a late model Shelby. I quickly realized how easy it was to overdrive the faster, newer car beyond my limitations. I think this '65 would be a HOOT of fun, and it seems quite streetable as well. The engine is mild, so it will be easier to learn how to drive fast with it. This car won't allow you to be lazy for even a second - where the speed can overcome your concentration and awareness of what's going on. You will be connected to it and the road in ways you have never experienced (I know you have a '68 and this car is a completely different animal). You will stink and need a shower after each drive, your neighbors will know your comings and goings at all times, and you will love every minute of it.
I don't think there is any comparison between this car and a new Ford/Shelby. They fit different needs. The new cars are a dime a dozen. I like my 06 Shelby, but I would trade it back for my '65 I had in a heartbeat. I had much more fun driving the old fastback. When properly set up, these older Mustangs are really fun, they hold their value and the smiles they bring to the drivers, passengers and observers are unbeatable. The only car that I've had more fun driving is a Cobra roadster.
Hard to tell on value, but if you could buy this car for $40-$50K from a proper owner like this I think you are in the winning range. You may have to spend more if you really want it (nothing wrong with that), but there aren't too many good examples out there with known good histories offered by their owners.