Lose the tach. Don't need it in my opinion. Just another useless gauge that's not going to get looked at until after the race when you hit the recall button, then it will tell you that you hit 10k on the start.
If she's watching the shift light, she's either going to get run over or run someone else over. Gear indicator I'd maybe go with, more than once I've wondered why my car sucked after a restart only to find out I was in 5th instead of 4th, but not a shift light.