Jesse,
If you are wanting to keep the high FOC you have with your carbon setup, then a 70/75 or 75/80 spine is probably what you are looking for. The old bear Razorheads are probably going to be in the 115 - 125 grain category depending upon whether you use the bleeder blades or not. I shoot a total of three hundred up front out of a 41# @ 30” draw long bow using Douglas Fir shafts. My arrows are 30 5/8” from valley of nock to back of a 100 grain woodie weight. My hunting partner is shooting the same shafts and weight up front at 29.5” long to back of woodie weight out of a Bear Grizzly recurve that is 45# at 28”. You are going to be shooting a lot heavier arrow with this setup. 760 - 800 grains.