Agreed definitely rats,definitely... heh
KMG is right though some can make the change over let than smoothly. It's all about the snake knowing what food looks like. I would suggest changing one factor at a time and not until you have a.. 120 gram animal to work with.
So I think a good plan would be to get him eating live rats. Once he knows that food smells like rats and is eating them without a problem, with live I've found the switch over to be easier. Then you can make the switch to frozen. Find a system that works for heating them to just a bit over live, they wont hold heat long so you have to feed quickly after heating hence the overdoing heat just a little.
I switched over from live to frozen about a year ago, it honestly wasn't as bad as i thought it would be and I save a ton of money on food because of rodent pro. Though feeding frozen takes WAY longer than feeding live.