OP should have fitted:
1701746 - timer
1702251 - heater
The thermostats on the heater box are (left) a one-shot safety and (right) a 109c operating thermostat. They are replaced as a pair, p/no 1701896. If the safety has failed, the disc on the front will be dished inwards.
The single commonest cause of failure is opening the door whilst the dryer is running at full heat.
Element failure is usually caused by foreign object damage, typically bra wires being forced through the back of the drum.