HD 10 would have a 4-71 GM, the HD 5 had a 2-71, HD 7 had a 3-71,10 had the 4-71 and the HD 14 had the 6-71 as did the HD 15 & 19. The HD 20 was the only one not to have a 71 series engine, it had the 6-110 in it. I used to operate an HD 14 in my early days. Cheers RDG.