I'd pass. I wouldn't want to own a truck with the 3V Triton engine design. Plus the price is too high anyway.

Ehhh it could be, that model has the dreaded spark plug issue. Make sure the owner has addressed that. Since it has higher mi it could’ve been taken care of. I’d only go 5 or 5 1/2 for it. Of course depends if the truck got a clean bill of health. I wouldn’t daily drive it either, just use it for a work or camping truck. 

That's a fair amount of money for an old F-150 that probably has a 3v.

I would do 6K tops if it was in nice condition

Don't get stuck with a beat up 3v. They can be fine if the owner did the necessary bulletproofing but the last thing you want is for spark plugs to start getting launched

Also, especially for a high mileage truck where there is no meticulous service history from the previous owner(s) (especially engine oil intervals which is absolutely paramount for the 5.4L 3V V8) I would say to avoid the 5.4L 3V V8 in order to potentially avoid trouble/headache later.  See below at 6:47 by Master Mechanic the Car Wizard

https://m.youtube.com/watch?v=u6Jx0dWLQSI