Here is one cheaper with free shipping in the states. The other one may have a terrif
https://bluestarperformance.com/product/heater-blower-motor-resistor-3847094-f-m-body-1979-80-nos/
This link shows 61 to 68 I think I seen a 69 one time with one
https://www.retromanufacturing.com/products/1961-68-dodge-d-series-trucks-huntington-direct-fit-radio
Black beauty is made from coal slag its for cast iron and will warp sheet metal a couple of other fourms talks about it. And any experienced sandblaster should know. Too bad it happened to you I would not be too happy either. Maybe you can find another cab with some searching