What might be a good offer for this II

I normally am not a biiig fan of IIs...but I do love the Machs/sportsroofs/cobras. I found one I am tempted to find the owner of and try to purchase. The car is a '77 sportsroof. It has its original green paint which has alot of surface rust but nothing too bad. Needs a new rear bumper. Has a 302/C-4. Car is completely stock. Here's one thing I really like. Nice fancy white interior...and the weird part is...its like no one ever sat in it. I cannot begin to describe just how good the interior of this car is...its like factory brand new which baffles my mind especially for being white. The car has about 70k miles and has been setting at least 10 years I know of. It's at an abandoned house and I think the owner left it at the old place to get it out of his way. Any ideas what a good offer might be? I say I could drive it home if I put some new tires on and got some fresh gas and battery.

Part availability is one reason I am attracted to this car. Every bit of its there, not a dent or ding just surface rust. Needs the rear bumper though. I'd assume it would need suspension/new fuel system, engine freshened up. But bodywork and paint could be done in 3 or 4 good days and once again...interior is flawless.