Tilt latches missing or broken

Concerning the release lever, I've never known these to be left/right exclusive. These are pretty much all neutral without any exception I can think of. The same cannot be said of the internal latches themselves, which do usually come in explicitly left/right pairings.

It should also be noted that you can't really just put anything on that window. You also can't install anything in your window other than the exact latch you have now. These are very specific and there isn't any room for alteration. You will need the precise size and spacing of those forks in order to identify the proper match. There is no other way to size these. If you can't measure those forks, you won't be able to find a good replacement. 

If you are looking for a generic option to get around having to find an exact match for the existing hardware, then you should consider changing the entire tilt latch setup with a surface-mount style. This is a pretty handy solution and works on most tilt windows. You can see our full selection of surface-mount latches here. We also have a video guide that show you how it's done.

You basically just need to find a surface-mount tilt latch that will fit on your sash and whose installation holes won't interfere with whatever holes are already on there. We have detailed dimensions for each latch in our inventory that you can use as a reference to find something that will fit that criteria.

You're definitely on the right track. If any of the holes in the new latch overlap with the old holes on the sash, then they are not usable. You will have to discard the 26-178 as a possibility.

That's the trickiest part of this whole procedure. You need to find something that will both allow your latch to line up properly and avoid any holes already existing in your window. There is no trick to that, you just have to check measurements until you find something that fits the bill. You also have to consider, though, that there may not be a latch that fits that criteria. Your window was not adapted in this way, so a perfect fit isn't guaranteed. Just something to keep in mind as you move forward.