Since we're in a similar zone I'll post my results even though I don't shoot GTs.
My Sas is very spine tolerant and I've shot carbon/aluminum/and wood out of it. 63@31 so it's just a bit heavier than yours.
The best arrow I came up with was a CE Heritage 250 with a 75gr insert, and a 225 TuffHead. That effectively gives us the same tip weight. According to CE's website the 250 spines at .391.
I originally thought I'd be able to go with a CE 350 with the same weight setup. It shot pretty well, but the 250s were always a little bit tighter. The Heritage 350s spine at .324.
Given you will be at 55#, I'd wait for the bow to show up and try the 5575s full length. If they are too weak, how much could you shorten them? You're a long draw guy so there might not be much there to work with.
I'd send you some CE 250s to try out, but I just put them on the St Judes auction a few days ago.
Oh yeah, WE NEED PICTURES!
Thom