Here is my advice. Put the original engine back in the Impala, swap the 350 into the truck. The Impala will be worth more, and the truck probably will be, too. It will be easy to detail the 350 to appear like a 283/327.
I'm a fellow 65 Impala owner, btw. Numbers matching, 327 4bbl.
http://s40.photobucket.com/user/jayo...9pkjr.jpg.html