Apple rootstock for Leelanau
I reached out to the staff at MSU Extension's Northwest Horticultural Research Center in Leelanau County. They said:
"It will depend on your soil type and site. My guess is that you will want something that is cold hardy, disease/pest resistant or tolerant, and suited for sandy soils. I would not suggest bud 9 as it is a fairly weak tree on sandy sites and requires a good deal of care. Replant probably won't be an issue if it is a virgin site."
They also suggested this website: https://www.summittreesales.com/rootstock-descriptions/apple-rootstocks