Right now, I have about four fat bundles of wound up wire under the dash of my 39. The difference in price was so small that I thought what the heck. I will have to go back and remove a few circuits. I know I will never have electric seats, or A/C in in. A sound system besides the engine may find a way into it one day, so I'll keep those.
Now I think about what the car will really need, and buy accordingly.
I'd say remove any circuits that you know you will never use, and hide the rest until you are ready for them.