My subs, I believe, have some how manage to damage the top part of my dash and there is now a big crack in it. What do I need to get so I can fix that and stop it from cracking even more?

 

so what you are saying is you have subs mounted in your dash, pics??

 

dashes crack

Jacking the truck up in the wrong spot can flex the dash weird, or heat expansion can cause cracks...I wouldn't blame the subs..