Clementine link is here:
http://www.diytube.com/phpBB2/viewtopic.php?t=4893
You can use 6V6GTs in a Clementine socket with no mods to the socket (same pin out as a 6L6). You will need to change your bias resistors (higher values that will need some tweaking) and the B+ needs dropped about 100V with a different transformer. These changes and the testing that is involved does kind of lead back to what Tom was saying. If cheap tubes are needed, Russian 6L6s are peanuts last I checked, and very linear tubes.
Shannon