The big mistake is putting a p.o.s. Chevy engine in a wonderful Mopar. All the Mopar guys will hate it, and think you are an *** for ruining a nice car. What the he'll are you thinking? Jmo.
Your car, your plan. If plan on keeping the car forever, do what you want. Sell the 340 and swap in the chevy motor if that's what floats your boat. Value means NOTHING if you never sell it. Don't base your decision on what other people tell you.