The Ace 44's have an 8.25" axle and that's what I am running but I usually ride between 8-8.25" boards. The 55's have an 8 7/8" (8.87") axle so I don't think you are going to find Ace's that will be perfectly flush with an 8.5". The difference is negligible and you should be fine either way. If you dabble in wider boards occasionally go with the 55s, if narrower boards, go with the 44s.
If it was me I would go with the 55's in your situation figuring that a little wider isn't going to hurt anything and may feel a little better on a wider board.