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
You may have to do a lot of searching online I have been there many times. Here is a good read on 351 and 400 if you read the whole link
https://fepower.net/Products/feia.html
Sometimes the dimmer switch will cause headlight failure and make sure the cab is grounded and disconnect clean the balk head connector where it enters the cab at the firewall for starters...