Even though it's not an HO or 400 drop top, I would think always having the original drive train would make it a little more valuable.
I would rebuild a different engine and store the original. There's no shortage of 400 cores around. It would suck to rebuild the original and have a rod go through the side of the block.
For $5K you can build a hell of a 400 and still probably have enough to get the 350 back to specs.
