Hey I’m putting a sub in to a 2010 model and want to get a 12 volt source from inside the cab instead of pulling through a firewall into the engine bay, any ideas?

 

There wont be a 12v source in-cab able to carry the amperage. Even with a Class-D amp only requiring a 12 or 10 Gauge power wire, I would still run it to the battery. The only amps that could really stand a chance to run off radio power/fuse box feed would be the small 4 channel Class-D "brick amps"

If its a Class A/B, forget about it. Unless you want to blow every fuse and melt every wire in the cab.

 

And make sure you put the fuse/circuit breaker as close to the battery as possible.