UPDATE:
The lug type I'm looking for is the one on the left - it's from my 50's Cadillac Green tom - they may be the same as the 60's lugs. The lug on the right is from my 2011 Custom USA rack tom - notice it's hollowed in the guts of the casting - it also has a more bell-shaped top end profile (photo 3).
1 5/16 center-to-centre on the mounting screw-holes and 1 15/16" overall length.
I'm still looking for l6 lugs and mounting hardware that I can fit to a 6.5" snare drum.