Fox body for '69 GTS trade, Opinions needed

Hey guys, My father has a '85 Mustang, LX 5.0 5-speed, 36k miles special order car, found it in a barn last year. Runs and Drives great..100% the way it came from the factory. Last year for a Carb on a Mustang..

His Friend has a '69 Dart GTS 340, California car runs and drives, but has a tick in the motor, so will need rebuilt. Pretty much complete, buckets are ripped, looks like the car may of been hit before and repaired, front looks a little..off if that makes any sense, and someone welded the hood bulges to a flat hood(did a pretty good job doing it though) car is very solid was a 340, Auto, A/C car

My question is, would this be a fair trade? Hes asking $5900 for the Dart, and we figure the Mustang is worth between 6 or 7...but i could be wrong, what do you all think?