I have a Frank San Marco Hill style bow it is 68" I draw 27.5 and get 47# am wonting to shoot 125grn points. and a total weight of 500grns. Thanks Cecil

I would start with a 50-55# spine, with a tail taper down to 5/16".  On the Hill style bows you don't need to go much over your bow weight on your arrow spine.

Much depends on how deep the shelf is cut.  A FSM is going to be 1/8" or more out.  I generally find Hill styles to shoot at or a little below draw weight with a 28" arrow, 125 gr point and a dacron string.

I'd say you got your answer. 50-55 should do it with a 125grn head at your draw length and the Hill style bow. I draw 25 1/2 to 26 and my arrow length is 27" to back of point. I shoot 50-55 spine from all my longbows from 45 to 53 lbs. with 125 up front. Works great for all!