Congrats to dsquaredd2 for the FTF!
Cache is NOT at the listed coords.
You will have to solve the below puzzle to obtain the correct coords!
Once you solve the sudoku puzzle above, you will need to do some simple math to obtain the coordinates.
N 39° 45.GHI
ABC + 492 = GHI
W 076° 39.JKL
DEF - 571 = JKL