I got a 27.5" fork for my 26" bike, what size wheel should I run? I have an Ellsworth AM bike that's running a 26" rear wheel. I just scored a great deal on an x-fusion sweep fork that's 160mm travel (same as the frame) but for a 27.5 wheel.

I am in search of a new wheel for it, and I wasn't sure if I would be better off running 26" wheels all around, or if I would be better off running a 27.5" wheel up front with a 26" wheel in the back.

Just looking for some advice before I bite the bullet on a new wheel.

Thanks!
You probably have a different offset and a different fork height now, so whatever you do, you have already messed with the geo noticeably. 

Borrow a 27.5 and a 26 front wheel from a friend for a day, go ride, figure out which one feels better. I would guess 26 would feel closer to how it used to but it should still handle differently due to the different offset, but who knows you might prefer the 27.5 even though that should leave your geo even more altered :)