318 or 340?

I was in the market for an engine when I heard a Dodge Ram with a 360, cam, exhaust some simple stuff ohhhhh boy. I can't freaking wait to get the valiant done and put in a 360... Deals can be found, lots of durangos are out and about.. In my area it's 500 for one with a bad tranny, I managed to get one for 400 good everything just needed a ECU. Worth the peace of mind knowing it runs good before you put in the labor.. The main thing to plan for is cracked heads, I've heard it's common in the 360 magnums