So i can tell you by my green truck,that is a 72 model i think the rear is a 4.33 and it works really well,the red one on the other hand had the 1300 and it has i believe a 4.88 so if i keep it i will change it out.I think all the 1600 models came with the 4.33 or close to it,can some one validate or correct me please.