I'm not sure I understand what you are looking for? Engine doesn't change rpm, and also you need to specify what gear you are looking for.
And with a 6sp, just multiply the 60 speed by 1.33 and that will be rpm at 80, assuming you are in the same gear. With auto, there may be slip if the converter isn't locked, but assuming it is, all straight math, but you need to specify which gear.