I also noticed two distinct variations on the R series front sight. As we all know, R series front sight lacks the "Z" spring. Well, there's one version that has the provision for it. Looks like this was a transitional version and was decided later on it was unnecessary.
The "Z" spring equipped SA sight have squared corners and rounded on the non equipped variant. I also found that the easiest way to install the front post if you are upgrading to the thin R series is screwing it from the bottom of the front sight assembly. Screwing it from the top is almost impossible to do due to how the legs of the post is spread out. Save yourself the trouble, install from the bottom.
I acquired this R4 gas block(thanks to WILDCARD!)which I believe again as a very early version not like on Lou's R4 which I think is a later version. It's almost identical to the Galil with very minor differences. Most significant is the width or length of the sling loop depending on how you look at it. The R4 is a tad short compared to the Galil.
Galil is on the left with front sight assembly installed.