I have a musty, "mousy" smell when I turn on my heater or AC (1965 C20). I think that when my truck was in a barn for two years waiting for me to buy it some mice got into the heater hoses and did their thing. I am wondering how I can remedy this. I have heard that I can spray an antibacterial spray (like Fantastic) into the cowl with the blower going and the spray would get sucked into the hoses. Has anyone had experience with this?

1965 Chevy C20 Stepside