Heater resistor?

I’m troubleshooting a few small electrical issues with my newly purchased 67 barracuda.
One of the last issues is that the heater blower isn’t working. I pulled the heater box when I bought the car (it had a big mouse nest in it) and put all new gaskets, etc in the box. While out I put power to the blower motor itself and it ran nicely with the squirrel cage on it.
Now that it’s back in the car, when I turn on the fan switch I get nothing.
I got under the dash with my power tester and I confirmed that I have keyed power to the switch (black wire) and when the switch is on low I have power in 1 wire to the resistor, and if I turn it on high I have power to the resistor in the other wire (green and brown to the resistor).
So I’m pretty sure my issue is the heater resistor; is there a way I can test it to make sure it’s the resistor?
Are resistors available out there or are they tough to find?