This is right out of my manual
"The wax filled thermovalve is mounted at the top of the radiator sensing
coolant temperature. The thermovalve controls the action of the switchingvalve. When the radiator is cool the hydraulic fluid is allowed to flowthrough the inlet and outlet ports of the thermovalve and return to thehydraulic reservoir. As the coolant temperature inside the radiator rises toapproximately 185° the wax inside the thermovalve begins to melt and
expand. This begins to restrict hydraulic fluid flow through the thermovalve. The restricted hydraulic fluid pressure then begins to move the internal spool valve of the switching valve. The process will continue until coolant temperature inside the radiator reaches approximately 199°F. At this temperature hydraulic fluid flow through the thermovalve is stopped, moving the spool valve to full open position"
Whether you can use a different thermovalve, my guess is yes, it will just change what temperature your system runs at.
My thermovalve is B5531-09857-210 also. My engine normally runs ~183F but will go up when pulling a grade.
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi