BlueBill:
Thank you. I guess the choice is a 100ohm resistor & Schottky diode clamp to 3.3V or a 3.3V 433/315 MHz module.
There is also the method of just using a high enough ohm series resistor between the 5 volt signal to the input pin that will limit the current flow to a safe enough value to not damage the now conducting high side clamping diode. I don't recall what that value is for a 5 volt signal using a Vcc of 3.3 volts, but it is a valid method to use and have seen it described in various AVR and PIC application notes I've stumbled across in the past.
Lefty