I think I finally have it! I downloaded CushinForDaPushin & bob322's Dually Sandking as it looked like a simpler mod than some I was finding. I swapped out the ytd and yft files for ones from the granger and changed the names to the ones of the dually sandking. It spawned in but had no sound. Edited the sound hash line of code to the one of the granger and that fixed it. Next I swapped all the names and it spawned in and registered as an SUV now!