What are the best needles to use for oldschool tattoos?

It's all a matter of opinion, but for more traditional tattoos, you will want to use a thick line which means that you will want to use nothing smaller than a 7RL. Having a smaller outlining needle is not really needed since there is very little emphasis on varying line value with these kinds of tattoos. For fill, you want to use judge that more so based on the size of the piece that you are doing. Once again with these tattoos, there is not a lot of emphasis on saturation of great blending, so for the more "traditional" look, a small to mid-range mag needle is the most used.