Bob, the small block Guzzi's are a class unto themselves. Can't say I've ever seen or read that. So, I pulled out the Guzziology and sure enough, in Chapter 13 under Lubrication there are several paragraphs about adding moly to the rear drive.
Dave Richardson, the author, writes, "...we have found an appropriate additive....made in Seattle, alled Power Punch EP-1." He goes on to say that he uses moly with non-synthetic gear lubes (or Amsoil) in motorcyle rear drives.
Small Guzzi twins like your Lario use 160cc of gear lube and 10cc of Moly, total capacity of 170cc.
You can order Guzziology on line. Not cheap but an excellent companion to your owners manual.