I am in the process of rebuilding my 98 Dodge Ram 1500 3.9L engine. I took the heads to have them rebuilt and found both heads were cracked on the last cylinders on each side. So started to look for another set of heads and the shop that was rebuilding the heads for me said to make sure I found magnum heads. That the 3.9L was a magnum engine. Is this true are the 3.9L a magnum engine? There is none thing on the truck or engine or under the hood that spells this out.