A mounting plate assembly for use in aligning electrical and plumbing components of a toilet flush valve installation includes a pair of rails having openings therein for use in attaching the assembly to wall studs of variant spacing. There is a plate with openings and fasteners on the plate and rails for variable mounting of the plate to the rails. The plate has an opening for installation of an electrical box and at least one opening for a water inlet pipe. A pipe locater is used to properly position a pipe within the plate opening. There are openings at upper and lower portions of the plate to insure its correct vertical alignment with a water drain from a toilet fixture.