Big Larry can chime in here but I believe they are same, GL-vs-B...Yes Progressive does sell a lowering mono tube , I had them in my B but the springs to my knowledge are the same !
+1 and the OEM GL/F6B springs can also be used in the VTX1800 forks too.
The guy who invented the first wheel was an idiot -
the guy who invented the second one... he was the genius!