For $160 + shipping? Nah, I'd pass.
Besides, that "conversion kit" looks like it's just a pair of OEM NB rear upper mounts. You could probably pick up the same thing from Mazda Heaven or somewhere for a lot less than $160. Heck, I got a full set of OEM Bilsteins, OEM Sport Package springs, and all four upper mounts, all assembled, for only $200. You could buy something like that, then turn around and sell the Bilsteins & the springs to recoup most of your cost.