after some looking found a past post from Alan about this he says:
"All three tubes are the same.
All years of tubes 70-74 are the same.
No lenses ever attach to the tubes."
also found more info
"All three tubes are notched differently, but the notched tubes were never used for attaching the lenses. The lenses are directly attached to the bezel, which is notched as well....all three (left,right,and brake are notched with a different pattern). For some reason I was under the impression that the lenses were attached to the light tubes. Even though the tubes are notched, the lenses were never attached to the tubes. So,a set of aftermarket tubes that are all notched the same (or not at all) is not an issue"
"lenses/tubes go L, R, Brake"
so I guess the lenses attach in side the gauge housing and the lens do not fit into or attach to the light tubes.