Gear ratio recommendations?

[mcbassin]

I recently drove my truck for the first time with this setup. It has stock 4.8, 4L60E with 3:08 and 275-60-15 on the rear. It is a slug at best. Seems to need to wind way up to get going anywhere. I was thinking of going to 3:73 initially but I found 4:10 stock axle locally that would be a plug and play. Is this too low?
thoughts?

I want better low end power but I'd still like decent mileage at 70MPH.