CAT 3126 (Stock #33234) | Fuel Gear Pumps | TPI 24 July 2017. Image Subject To Change.3126 Caterpillar Fuel Filter Truck - Montana Work Comp Class Codes. Need to find Montana workers compensation class codes?Montana uses the NCCI classification system. NCCI stands for The National Council on Compensation Insurance. See the applicable list below. If you have a classification question or believe you have been incorrectly classified, please see The Employer’s Workers Compensation Classification Guide..