TKO 600 for sure.
Your cam will determine whether or not your motor will be happy at 1600-1900 rpms or happier at 2300 for cruising. I have a mild cam and can cruise at 2000 happily. I enjoy my .64 OD but the rpms do certainly drop. It's just for the highway-if you're racing and for some reason need to use 5th, you will lose and .64 is not right for your usage.
I never need 5th on the track, so I'm fine. And you
should be too.
With the stock 3.73 rear end, my 1st gear is useless. Your 3.54 will be much better.
But I get 20.02 mpg's on the highway with that .64, which is better than the wife's Explorer!
