I would pick the Remington 700 to customize just for the fact that their is so much aftermarket stuff out their for this rifle. I would hate for you to part with the Weatherby 270, it's a very nice rifle but I've been their, done that, so I know what you mean.
Question, what is your goal! Accuracy, looks or what, that makes huge difference in why you want to go to this kind of expense.
dbuck