To Restore or Not to Restore

If you're trying to restore it as an investment then the way to go is to make sure everything is correct and documented. The money in resale is primarily for the most unadulterated documented cars. Big block cars should have all of the "big block specific" parts including the correct exhaust manifolds, oil pan, air cleaner, Z-bar (if it's manual), radiator, etc.. to retain the greatest value.
It looks like you're off to a great start. Keep the updates coming.