Actually, in Colorado, your vehicle needs to be pre-1976 to get a collector plate(used to be 25 yrs or older). In Larimer the emissions zone goes west beyond Bellvue. With a Comanche, you can get farm tags for a truck IF you have acreage and are willing to sign an affidavit that it wil be used primarily on the farm.
I have a 90 Pioneer and it doesn't have a check engine light. No pre-OBD system does, only a mileage related advisory light to get your emission system checked. It is not a "learning" system. Had to educate our local emissions station since my truck had just passed 75,000 miles (mileage trigger) when I bought it. It took about 10 extra minutes for them to call and self-educate. No problem
They did a visual and idle test.