The main places I'd want my gears lower would be 1-4 I would think. The mountains I'm not running up at 80mph, usually speed limits are like 65 in the mountains or less so I'd be able to use lower gears. I would think a short 5th would just suck gas down at all times. When I had the hch trans I was pretty surprised how much it made it accelerate better if you shifted at redline. It actually pulled decently hard. I'll probably need the slightly shorter HCH final but I'm hoping not because that's going to use a lot of gas at 88mph.