Iride01 V brakes of any flavour are compatible with the same mounts as 'centre pull' cantilevers that were the dominant brake up until Vs were introduced in the mid 90s. Pivots on a 1999 mountain bike like the OP's will 100% be compatible with any V or mini-V brake. There are some differences between different bikes in how the pivots are spaced and positioned, but this can be handled with spacer configuration and pad positioning on the brakes. A much older bike (mid-late 80s) might have weirdly positioned brake pivots compared to a more modern bike, but even these can almost always work with modern Vs and mini Vs if the adjustments are done properly.