Hello,
Is this normal for an older chevy box truck g30 high cube? I have never had to use Dex-coolant. Also I can't get the coolant cap off so I've been pouring coolant in the overflow tank.

Thanks in advance,

 

Looks pretty rusty. I'd use an alkaline cleaner to bust all the rust off and out of the motor. As for your radiator cap, try hitting it with some piece of wood on top and a heavy hammer. If that doesn't work use an adjustable pipe wrench on it. Maybe hit it with some penetrating spray beforehand. Are you having overheating problems?