Having just been through this exact issue with DMV registering my out of state vehicle I have a little bit of experience. It is plainly stated in the DMV handouts that diesels over 14K are smog test exempt even though the DMV employee thought otherwise. The girl who inspected our MH for the VIN inquired about the smog label, found something in the generator compartment which satisfied her and completed the process. If I were in your position I would take it to DMV and have them inspect it. That needs to be done anyway for the VIN if it hasn't been done already. The requirements for the CARB label are buried inside DMV rules under the state Health and Safety Code. If yours does not have such a label you may be forced to contact the engine mfgr for a label. There are exemptions to this rule that you may qualify for.