I'm pretty sure the mounts are the same between the SI - IV. . . . but as said before. . . the aesthetic fitment might not be the same. . . but ya can get around that, some people just install a piece of rubber in the gap and it works a treat.
If your getting it off a DX and putting it onto an ST, just make sure that it's the bar that suits wheel flares. . . There were two different bars made for the pov packs without flares.