It may have a 14b rear, but there is no such beast in the front....
Is it 8 lug or 6?
all blazers are 6 lug stock.. 1/2 ton stuff.. stock rear dif for that year is mostly likely a 12b.. front would be a dana 44...
installable rear diffs could be 10b, 12b, 14bsf (6 lug or 8), 14bff, dana 60, dana 70, etc...
fronts could be 10b (6 or 8), dana44 (6 or 8), or the holy grail, the dana 60..
someone may have thrown some 3/4 ton gear in there.. 14b rear and a dana44 or 10b front in the 8 lug variety...