ok so after debating with kyle, i looked up the EMPI part #'s and searched em out on ebay, where i found the manual trans axle to have a 14 7/8" inner shaft and the auto to have a 15 5/16" inner shaft.. so thats probably whats going on, thats like almost 12mm difference, even tho we're only seeing about 4-5mm difference..
so make sure you get axles for the right one! lol
i did do research an from what i found was that auto an manual axles were the same for sr20de as long as BOTH were either LSD or open diff, not sure if that applies to oem axles or what.. any how thats what i found, figured i'd report back.