You might want to go with the 5-ton truck; the V150 shares a lot of drivetrain components with those -- handy for post-apocalyptic logistics. Or the HEMMT -- some versions come with a handy cargo crane.
http://olive-drab.com/idphoto/id_photos_m54.php
http://olive-drab.com/idphoto/id_photos_hemtt_m977.php
http://olive-drab.com/idphoto/id_photos_hemtt_m985.php
7 people with an M102 leaves no more than one person to operate an FDC, act as a radio operator, and as a forward observer. And the unit still has no innate security when it's emplaced and ready to fire.
Instead of the ancient Priest, how about something newer:
http://olive-drab.com/idphoto/id_pho...8_howitzer.php
For that matter, if this a one-of-a-kind thing, why not just make a custom vehicle, suited to the Morrow Project?
Or: variations on the M113A3 'Gavin' APC. The proposed M8 'Buford' AGS (armored gun system) had a 105mm autoloading gun, woot. And there's been discussion of a hybrid electric drive version, which would make a Morrow Project conversion as simple as plugging in your fusion pack.
http://www.combatreform.org/hybridelectricdrive.htm
(note that the author of the "combatreforms" pages can get mighty worked up about his favorite topics, one of which is the M113)
Imagine a hybrid-drive version of the M8. The Project could just snap them up and roll them right into a bolthole.
http://www.fas.org/man/dod-101/sys/land/m8-ags.htm
--
Michael B.