Rear gear change question

[Caleb]

well im new to the forum so if i posted in the wrong place please forgive me. i tried to navigate best i could. anywho main point. i have a 1984 GMC K1500 with a GM 12 bolt and im looking into a rear gear swap . i did some research ( im mostly self taught because my dad is at work) and im still fuzzy. i get there are different series carrier and gears for a GM 12 bolt ( 2,3,4) if im not mistaken. i get i can get thicker gears and ring gear spacers. here is where it gets tricky. i want 3.73's in it (4 series) and i have 2.73's (series 2) in it now with an LSD. but on the factory sticker in the glove box(with all the parts list and stuff) it says it came with 3.08's (series 3). sorry for the jumble of info im just trying to give you guys best description. so my question is what are my options for putting 3.73's in. what carrier is installed? series 2 since the gears are? im confused and i dont want to go down the wrong path since these things arent very cheap. thanks guys.