cherrybim: It is unclear what Rav Moshe upheld regarding a cul de sac. I have heard arguments both ways. For whatever its worth, I believe that Rav Moshe would allow.
According to those opposing the eruv besides for cul de sacs there are no other streets that would be allowed according to Rav Moshe, hence there are no other streets to omit from the boundaries of the eruv.