Hi Skyler. Take the above responses with a grain of salt - many purists are predisposed to be critical of any modified Chevy truck. I have never seen a positive response to a "should I buy this" question. You could post a brand-new showroom fresh AD and some folks would find 20 reasons it was unsafe and say it's only worth $800. Just typical of forums, I guess.
It's a normal procedure to put later model GM front suspensions in these trucks; there are thousands of them on the highways today. With IFS, power disc brakes, power steering and a V8, your truck has the potential to drive much faster, safer and better than any original or restored AD truck. The previous owner put nearly 4000 miles on it so it's proven itself that far anyway. That being said, that Le Mans clip looks like it's poorly grafted to the original frame (photo 102). However it also looks like something a decent fabricator could safely rectify in an afternoon. The price is high, but that's typical for any dealer to start high to leave bargaining room for offers and trade-ins. If it speaks to your heart, make them a lowball offer; you'll savor every minute and every dollar spent fixing it up.