Jeff, Using the registry, compare the manufacturer construction numbers with the US Navy serial numbers, those before and after. They do fall in line with this being built as an AT-6D that was transferred over to the USN as a SNJ-5. Also you can reference Joe Baughers website at:
http://home.att.net/~jbaugher/thirdseries5.html which also shows it as such.
Your photo plane in question is N3258G it is:
mc/n 88-15924 to Navy as 43839
mc/n 88-15903 to navy as 43818Registry
mc/n 88-15904 to navy as 43819
mc/n 88-15905 to navy as 43820
mc/n 88-15906 to navy as 43821
mc/n 88-15907 to navy as 43822
mc/n 88-15908 to navy as 43823
mc/n 88-15909 to navy as 43824
mc/n 88-15910 to navy as 43825
mc/n 88-15911 to navy as 43826
mc/n 88-15912 to navy as 43827
mc/n 88-15913 to navy as 43828
mc/n 88-15914 to navy as 43829
mc/n 88-15915 to navy as 43830
mc/n 88-15916 to navy as 43831
mc/n 88-15917 to navy as 43832
mc/n 88-15918 to navy as 43833
mc/n 88-15919 to navy as 43834
mc/n 88-15920 to Navy as 43835 Registry
mc/n 88-15921 to Navy as 43836
mc/n 88-15922 to Navy as 43837
mc/n 88-15923 to Navy as 43838
mc/n 88-15924 to Navy as 43839 Registry (your photo)
mc/n 88-15925 to Navy as 43840 Registry
mc/n 88-15926 to Navy as 43841
mc/n 88-15927 to Navy as 43842
mc/n 88-15928 to Navy as 43843
mc/n 88-15929 to Navy as 43844
mc/n 88-15930 to Navy as 43845