when determining length of pull, first i would ask is the rifle for target or hunting. if it's for hunting, remember the thickness of your hunting jacket. the rifle i use for hunting has an 1 1/2 in shorter pull than my target rifles.
when finding the correct drop, like before mentioned, visit a match or muzzleloader shop to "try them on" stand in your shooting stance with rifle at your waist. closr your eyes and bring gun to what is a comfortable position. then, without moving, open your eyes. if you have to move your head up or down to see the correct sight picture, the drop is not the best for you. when you find one that is just right, trace it on a pice of stiff paper for measurements.