Scott, your placard(s) should be in the standard location, low on the streetside wall just behind the driver’s seat and any left side console. There’s likely a placard for the chassis (Magnum) build and another for the coach entirety. The pressure numbers there may not necessarily mesh with what your tire dealer or the manufacturer says, however, especially if you’ve changed tire load ratings.
That’s another good reason to get an RVSEF weighing before too long so they can give their best recommendation. 100psi all around is a safe enough guess, but hardly very specific to your particular current configuration, and not the ultimate solution.
Joel