I seem to recall we had some discussion on the Howard 500 conversion of the Ventura into a high speed executive transport quite a while back, and while looking for some reference photos on another Lockheed/Vega aircraft, I stumbled upon a site that has a description, history, and photos of the airplane. IIRC @rob Lyttle was either working on a conversion or was wanting information on it, so I hope the old Mk 1a memory banks haven't failed me yet again. I think there are only two flyable examples in existence- both owned by the same person! I saw the 1st one built on the Dee Howard ramp in San Antonio when I was a teen- had no idea how significant it was at the time!
Mike
https://www.deehoward.org/the-dee-howard-legacy/innovations/howard-aero-innovations/item/howard-500
https://www.youtube.com/watch?v=WAvfJGCqE40
https://www.youtube.com/watch?v=m8YogYSBcmU
https://www.youtube.com/watch?v=6HBmeWL-or0