It should be plenty. First gear is already usable but I'd like to be able to stay in 1st just a little longer, and any decrease is highway cruising rpm would just be a welcome benefit.Going from 4.10's to 3.73's is only a 9% rpm decrease, is that enough to do what you want.
My main thing is, I don't want to give up very much acceleration. I'm used to the 4.10's and I love how snappy the truck is.
GB