GFTextWidth(gump_text) - Currently only supports 1 font, I've tried to update for the new font the client uses in updated clients but failed repeatedly mainly due to the fact that I can't for the life of me figure out how this function works.

Any suggestions on how to get it to support the newer clients font?

On the newer clients the fonts are a fixed width.
It should be as simple as Len(text)*width

I think width is between 5 and 10 pixels.

That's one of the ways I managed to fail =)