The water system upgrade is complete. A new backing plate was installed opposite the existing one, and the shelf for the pump was moved to this plate. Old piping was removed, new piping (shorter mostly) was added. The non-barbed connectors are an absolute pain to work with when you don’t have a way to heat up the piping so that it’s more flexible.
The bracket for the accumulator was then installed where the pump shelf used to be attached (even more holes drilled into a bit of wood that already had at least 10 holes), and with some difficulty, the accumulator tank was attached.
Pressure tested, and there were significant leaks from the threaded connectors of the accumulator tank. Looks like I didn’t have a sufficient amount of PTFE tape applied, nor did I have the connectors tight enough. Re-visited the main one to the tank, and that made things better, and then re-did the barb connectors a day later.