imak,

I haven't tested this mod with 1.3.7 but I would expect it to work as I don't think that any of the differences between 1.3.7 and 1.3.7.1 will affect it.

Just be certain that you are using the right version of split tax lines. Version 1.1 is for the 1.3.8 series of zen-cart. For zen-cart 1.3.7 the one that you need is STL v1.01

Let us know if you have success with it!
Alan