The new regulated bias supplies are straight forward to install if you can do easy soldering.
On my backplates, the new bias supplies would not fit horizontally. So, I had to stand them on endwith removal of one plastic flange and secure them with hinge angles and glue.
If you have a larger backplate, they should fit in. Either way, they will fit in.
Roger will send you the bias supplies with sufficient lead length and a new bias pot and schematic for installation. All is straight forward and takes under an hour to fiddle through for each panel. The price from SL is most reasonable in MHO.
Highly recommended to do this. My opinion is that new bias supplies provide almost twice as much bias output as the older unit and is ac input voltage regulated to boot.