What is the rpm sweet spot for highway driving

I want to change gear sets because the take off is sluggish. I also do a fair amount of highway driving at 70-75 mph. I'm really trying to find a balance. My car has a 318, Edelbrock 650 and small XE256 cam. Trans is 904 and it is not the low 1st. I have 4 different gear sets to play with. Here are the RPM vs gear ratios.

I guess the basic question is the title...What is the rpm sweet spot for highway driving?

Currently running 215/70/14 the spec sheet says the tires are 25.8 calculated at 70 mph.

2.76-2583
2.94-2752
3.23-3023
3.91-3660

Thanks Craig