I would have to say that is a good question. Most Trooper turbo diesels I see have the circular headlights and are the 1986 year model. But, in 1987 Isuzu changed to square headlights for the Trooper and if you were to see a 1987 Trooper turbo diesel I would beleive you would notice the headlights. I also have always wondered if Isuzu sold the Trooper with a turbo diesel in 1987. In my opinion I think they did but when compared to a 1986 model, a 1987 Trooper turbo diesel is extremely rare. I actually wish Isuzu would have had the C223 diesel available in 1984 for the first year Isuzu Trooper, instead of just the pickups. Instead of just the 1.9 liter gas engine, they would have had the 2.2 liter diesel engine as another choice. I really think that would have been genius, but what ya gonna do.