Hello Marv
The most elegant BP Boss upgrade I have encountered was on a series II Boss 6. The Reeves vari-sheave drive which was factory was replaced with Goodyear Pd herringbone sprocket and rubber drive belt. This eliminated a lot of rotating mass and improved surface finish. Machine was almost silent. This upgrade required installation of Hitachi vfd and brake. It also permitted single phase power. I will be installing vfd in a few days on machine in photos.

regards
jackson