Hi Kayaker,
If I understand you correctly I think you want a "Larch, transparent" texture set?
The texture set "Fir, transparent" should say "Spruce, transparent". We need to change this in our English files. You cannot make this change. You also can not edit the texture to create a "Larch, transparent" with the Dietrich's program. Currently there is only the one texture set that displays transparent wood grain.