I read on another post that at around 55-60 lb draw weight you should have 350 grain arrows. Are the arrow weights on the boxes?
There is wY more to arrow selection then just draw weight and arrow weight . But yes the GPI, and spine among other thing should be on the box.
Also the weight is often on the shaft. Spine will also depend on length and point weight. So a shaft might be 400 8.4gpi. The total weight will be the weight of the shaft, knock and insert and point. So that shaft 28 inches long would weigh 232 gr + 50 gr insert + 30 gr lighted knock + 100 gr point = 412 gr. That's how it's done. Buy a scale and life will be easier.
I look for the lowest GPI grains per inch shaft then as said the length of the arrow and pull poundage of the bow will set the spine. I add weight with the broad head and inserts to get to the best FOC I can get for the targeted overall arrow weight. I shoot a Easton Hexx 330 spine at 28 in /70lbs at 6 grains per pound I add 100 grain head and a 50 grain insert with a lighted knock I am at 420 grain over all arrow weight. IMHO that is the sweet spot for mass and kinetic energy. QDMA has some good articles as well as Hunters Freind under arrow