You have a 1 ton, so you might be able to get away with a lot more than others. The standards in the 70s and 80s were different in Ca those years, some on trucks that had the same equiptment. You truck was obviously used(and probably purchased as a trailering special), so you have to go with that when you go for smog. A ref might let it slide a little. You have a reason for a high GVW truck. I was sent to a "gold station" one year and they plugged in the code for a 1500 instead of a 2500, they put in a whole bunch of new parts and the state picked up the first $900. It did not run right,for 2 years, and I went to my regular station next time and he found the problem, I have passed the last 6 times. These stations can do this, CARB wants the big old trucks off the road. These trailer hauling trucks need the power, so you have to make it known that is what it is for.