Wow - without seeing that VIN plate, I would've laughed me arse all the way back to my car after seeing that trunk 'decal.'
If you're interested in picking it up, make sure to check the stampings on the shock towers (under the fenders) to make sure they match the dash VIN - otherwise, all that might be there is a dash pad from a Boss 351. If there's still a door sticker, check it too - although the shock towers will be the big tell. The car's been repainted, with the painter getting the stripes and hood TuTone completely wrong for a Boss 351, not to mention the honeycomb taillight trim shouldn't be there either. A repaint can mean that sheet metal was replaced.
Considering they've all been sitting outside and all the leaves on the cowl vents of the coupe, I'd expect rusty frame rails, rockers, floor pans & intermediate (back seat area), doors, cowls, trunk pans & drop-offs, taillight panels, rear cross members, and lower quarters - especially around the wheelhouse area. You can even see it starting in on the quarters of the "Boss 351."
That would be quite a collection if they could be had for cheap... won't be cheap to get back together, though. The owner should just let 'em go if he really cares about 'em. Otherwise, they're most likely just going to sit there and rot away.
I'm over $40K into my car (not counting what I would've paid for labor had I not done pretty much all of it myself) starting out with something as bad as I believe that Boss to be... and that's using a LOT of repop and restomod parts on a lowly H-Code. In order to retain any kind of value on those cars, NOS parts are in order with a professional restoration expert at the helm. A guy could spend well over $100K on that Boss 351 alone going that route, only to expect $60-80K return on investment at auction time.
Any or all of those cars can be like-new again, but it won't be cheap or quick by any means.