I know that the 01-02 bellhousings use an -8 AN size going into the bellhousing for both to and from, and the 03 fitting they got me at the dealership by mistake were -10's. I know the 01-02's are -8 internal O-ring fitting as the steel lines wouldn't fit mine so I went with braided hose instead and had to get -8 to -10 unions and make a custom -8 O-ring to -10 flared to hook-up my lines. My new radiator which uses the newer fittings(my 01 fittings wouldn't thread into it) are a -10 O-ring, same as the 03+ external tranny coolers thread size. GM makes adapter fittings that will allow an 03 bellhousing to hook-up directly to the 01-02 lines with no modifications.
I got some ORBxAN fittings and decided not to use them as they put a even bigger restriction in line....hope your fittings are better