I don't think it devalued the car, esp if the orig was a 2-barrel. I think the condition is more important on a 'non-performance' car like this.
From the listing:
'it was originally a 383 automatic with AC, the 383 was locked up but I had a good running 440 that dropped right in'...'still has the original 727 transmission'
If that is true, then it would suggest that the 440 is an internally-balanced, steel-crank engine, and not some smogger motorhome engine put in there. 66-older uses a different spline count on the torque converter, so a cast-crank externally-balanced 440 won't install properly, it would have vibration with the 66 converter. Also suggests that it's not a 70-71 HP engine, which was steel crank but externally-balanced. Yes, it could have gotten a special converter or trans front support, but it isn't mentioned.
I don't have any opinions on the rest of the car, the pictures aren't all that great...