Im not really saying the #45 is the way to go. Im not saying that I know it will even work. I havent tried that gas block/front sight combo. In fact, if I had to take a guess, I would guess it probably wouldnt work. It may work if you turn the flip up front sight around so it flips to the front, but again, Im not sure. There may be an issue with the 3 rail gas block fitting? I just dont know.
However, if it did happen to work, it would work with any SIR system that is made for a standard carbine length gas system. Those SIRs would include the #45, #46, #50 and #58mod.