[SFfiredog]

A 390 and a 427 FE have the same stroke so building a 390 to physically rev to 7000 to 7500 is no problem, and not that expensive either. A stock 390 crank can handle 7500 rpm if neccessary so all you would need is a good set of aftermarket rods and light pistons.
The question is, do you want to make any power at those rpm levels.
You stated that you want to cruise on the freeway at 2500 to 2850 rpm steady. The cam needs to be sized to be make cylinder pressure and flow to be smooth and not "jerky" or "cammy" at those rpm levels. It is not practical to expect a cam to work well at that rpm and also be able to pull hard to 7000 rpm.
Most street cams have a 3000 to 3500 rpm "sweet spot" (2500 to 5500 rpm or say 3000 to 6000 rpm)
Above and below those rpm levels a different cam would make more power.
For example, if you cam an engine to cruise well at 2700 rpm,
it will most likely make it's max hp by 5500 to 5800, let's say 425 hp. That's not to say if won't rev to 6500 rpm, but at that level it may only make 375 hp, with the power dropping every 100 rpm above the max hp number. It makes no sense revving an engine where it doesn't make power (road racing is the exception, where you may need extra rpm to allow for gear spacing in turns)
The small 4.050 also hurts high rpm performance of a 390.
High rpms and big power generally require larger valves, and large valves get shrouded in the small 390 bore.
HTH,
--Mike