A "could have been (?)" the 'Jagdchieftain':
http://arcaneafvs.com/chieftain_concept.html
http://www.secretprojects.co.uk/foru...peihu69i68hm62
I'm sure I read that it was / maybe still is a runner although it seems that the gun may have been a dummy.
A similar vehicle with two guns was built around the same time on the Leopold 1 chassis.
Second photo down here:
http://www.tank-net.com/forums/index...c=37398&page=3