Refreshing brakes - what should I look at?

So the master cylinder I removed had a plate on the back that appeared to hold the dust boot on. Of course, the dust boot tore apart when I took out the master cylinder. I am looking to use a 15/16” master cylinder MC36338 which has the right 4 bolt pattern, but no provision for the dust boot plate... no tapped holes. Am I wrong in assuming the boot was originally bonded to that plate? Could it be that over the years it fused there due to fluid leaks, rust, and/or age?