Thank you all for your comments. I've been trying to gain info on this engine for some time and this certainly helps. My '67 DeVille just works too well to go through the additional headaches and expense of a 500 swap. I bought it from an estate sale where the man who owned it bought it new, and used it little. No A/C and no radio, but it has cruise control that still works.
It's no "survivor" by any stretch. Clean enough to look really nice and rough enough to drive. It was repainted but the driveline has never been apart, and is original from the rear end to the carb. I replaced maintenance parts, threw in some basic hot rod mods and smile each time I see this twenty-foot black monster parked in my garage.
Having owned several muscle cars/hotrods, I've spent years and many thousands undoing what previous owners did to those cars. Other than an occasional broken rusted bolt, it's been a real pleasure to work on a car that hasn't fallen into enemy hands. I'll be quite happy with a balanced and blueprinted 429 with the usual tricks. Hell, I may even keep the "airplane" gears and take the car on roadtrips. Thanks again for your help.