position field problems in table that's a child in two associations

I have a table that's both a child in an Acts As List association and
also it Acts As A Tree. Problem is I want to keep track of their
position in the list and rails by default keeps track of their
position in the tree (it seems). Is there some incantation that will
allow me to do this? I'm thinking maybe I need to override the name of
the position field or something but I'm not even sure how to do that?
Thanks if you can offer any advise on this. -Michael