Making alot of power at a low rpm is not exclusive to forced induction. For instance, if you had a 632 cid BBC with a mild cam, it would quite possibly make 700 hp at a relatively low rpm. Therefore, you would gear it similar to a smaller engine with a turbo. Like I said, gear choice doesn't have anything to do with boost, however, the power curve may be a result of boost. If you had a turbo Supra with a big turbo, then it would be making power much higher in the rpm range and require a numerically higher gear. If gear was a function of the presence of forced induction, then wouldn't you need a numerically lower gear in that case?

 

It's VERY simple. A higher gear ratio means it's less stress on the engine. A lower is the opposite. Turbo cars can't use high gear ratios because there is too little resistance, causing the tires to spin. So then they switch to lower gear ratios, and trap high because of the power and length of the gears.

Are you kidding me..? Supras do so well on the highways because they have longer gears. Not only do you utilize all of the power, the lower gears add more stress on the engine, reducing lag. You DEFINITELY want lower gears with a big turbo. You want higher gears with a small turbo because you aren't making any power, just like NA.