Kevin: The supplier you buy the shafts from should be able to offer the correct spine with a little more information, e.g., your draw length, desired arrow length, desired point weight, type of string material, etc. You might consider getting a test pack of different spines. Assuming a standard point weight of125 grains, and a draw length of 28 inches or so, 45-50# will probably work. Might want to try a test pack that will give you spines 5# lower and 5# higher.
Regarding the grain orientation. You want to affix the nock on the arrow so it positions the parallel grain perpendicular to the side of the bow. Or, stating it another way, the Vs formed by any grain run out should be on the top or bottom of the arrow when it is on the string and resting on the bow shelf.
The end of the arrow with the most grain run out should be used as the point end. The grain run out is most subject to warping and can be straightened more easily on that end of the arrow. Can be done if it's on the nock end of the arrow, but that usually involves mashing the feathers. Of course, on premium arrows, there should be no or very little grain run out. If the grain runs completely across the arrow from one side to the other, they're better used as tomato stakes, but there is some of that bad wood out there so buyer beware.
The Vs, if on the top of the arrow should be pointing away from the string toward the front of the arrow. They should be pointing toward the string, rear of the arrow, if on the bottom of the arrow. In the rare instance in which the arrow might break, this orientation usually allows the splintered wood to clear the bow without hitting the bow arm. Good luck.