Like blue is saying if you don't have the heads and intake then you will see minimal gains with the cam, RRs and TB. The lower intake 5.0 HO intake is the first bottleneck on the 5.0s. It doesn't matter how much everything under it flows if the intake won't support it.
Now if you already have the intake and heads then I would imagine you would see gains. If you don't have the heads and intake I would wait until you have them to install the cam. That way you can do it all in one project. Keep in mind that the stock 5.0 cam is a pretty decent stock cam and there are lots of guys going plenty fast NA with the stock cam. How much you will gain in hp, mph and lower ETs I couldn't make an educated guess at though.