.... I think you might get the bow pulpit in under 90" on the trailer, but it will be close. You won't have any trouble sliding the mast rig
fore and aft to do as you suggest. You'll have to pull the rear mast support, but that's easy.
I have about the same opening you have in my "barn", but have been lazy and not put Muireann inside for the two winters we've owned her. I have plenty of space for her outside and, so far at least, she doesn't seem to mind.