I did the exact same thing a couple of years ago. My Dart is a mutt and the 340 in it wasn't original so I had no reason to keep it. Sold it to a guy who just had to have a 340 cause "they were the best engine Chrysler ever made" and I used his money to pay for part of my stroker kit. If you have a good running 340, I'd sell it while it is still in the car and people can see that it runs well. I shot a video of my engine running, including showing the dip stick and the breather cap while running. I sold it to the first guy who came out and looked at it.