On the same subject...I have a 340 I pulled from my 71 cuda, that I plan on replacing w/ a 426 . I have offered it for sale for 3K, but no takers and that's w/ trans and exhaust manifold...The chances are that I'll get into another project car down the road, and if I wanted to replace the 340, if I needed to, I'm sure would will be much more.
I have yet to see a 340 block offered by mopar.
Keep it!