" The Caterpillar C7 was designed mostly out of necessity vs. practicality. Caterpillar, needed to produce a new engine that was going to meet or exceed the Tier Ratings enacted by the EPA in 1994 to curb diesel engine emissions. The stricter Tier 4 emissions requirements went into effect January 1, 2004. The Caterpillar C7 was released in 2003, only months ahead of the Tier 4 ratings change, and replaced the popular 3126 model. Older CAT engines like the 3116 or 3126 were essentially grandfathered into the older tier rating requirements and did not need to be upgraded."
Looks like you're in luck.