Being that the car is not restored to stock (missing a very expensive rim blow steering wheel, radio, power disk brakes (manual disks were not available in 1969), correct exhaust, etc), and I cannot see it up close and in person to see what else is not original (front fenders come to mind right off the bat), or done correctly, I'm going to step away from any reference to what it's worth. Instead, I'll ask you what the owner is asking, and do you think it's a good deal or not, as that is really all that matters. Why do I say this, simple, because you are looking at it as an investment, when in fact all it is is someone else's toy they are looking to sell. I'd love to see the Kevin Marti report as that will tell you exactly how it left the factory (forget about what a dealer may or may not have installed at the moment). Finally, getting back to value, does his asking price reflect a car that has been restored to stock (seems to be), or does it reflect a car that has not been, as the stock restorations (even a driver class car which from the looks this one is a step above that in overall condition due to some creative detailing) are what seem to be holding their value while the others are on a decline.
Might want to educate yourself on the 69 GT's by checking out the following urls:
Welcome to the 1969 Mustang GT Registry Page
1969 Ford Mustang
www.1969stang.com - Home
Bill S.
PS: Personally I'd be looking at BOSS 302's (driver class) or Mach I's in that price range.........