I know this has been voted on, and it looks dim, but.......
Great Idea.
These are two different cars, both with their own specific parts and have separate sub forum sections anyway.
Also, the fact that more and more 370Z owners are joining up is a key factor in this I feel.
Simply putting 350/370Z in the title isn't good enough, the key factor in this for me is that for every 370Z specific item that is posted about 50 350Z items are posted and often get lost down the board within a day.
I don't see the issue in having another sub forum to organise this better. After all, the sub forums/board index is there for that purpose anyway.
Universal items then yes, these should maybe stay in whatever section they are advertised in, so say if I want a gear knob and understand that these items are universal then I would also check the 350Z section.
I believe doing this would increase the functionality of the forum for the 370Z owners - like me.