The original nuts are 3/16" thick so you are good with those lock nuts.
The cover is removed by carefully bending back the turned over tabs around the base, I use a small set of end cutters
Just disconnect the regulator from the terminals and remove screw from the base and you have the regulator off.
mount DVR on the base and solder wires to terminals.
Easy.
I use the RB108 in original form with no issues.