I have a bypass thermostat on my 235 and have it installed as Roy suggests above with a tee in the heater return line. Works fine.

Both of the hose fittings on a dual fitting water pump share a single chamber inside the pump just like a single fitting pump.

Your heater return line is probably 5/8" heater hose. 3/4" brass PEX fittings available at any Home Depot or Lowes fit that size heater hose perfectly to make the tee.

Matt