Had a look at your picture on FB, you wouldn't happen to be related to Bec Seekamp would you? I knew her in high school and her older sister went to school with my sister.
Anyways tidy looking ute. The LWB is a great ute, got one myself!
GX Block would have flat tops, front dizzie and a unique water pipe into the side of the block. Yours has dished pistons, front dizzie and the water pipe has been cut short.
A12T had dished pistons but the dizzie was mid mounted.
Apart from that, unfortunately there isn't much more to prove that it is a GX block as they didn't have too much extra.