IMHO Israel probably would not want to hit Mecca. The Samson option would be utilized to STOP the Arab armies from overrunning Israel, before the major population centers had been occupied. If there are appropriate choke points or concentrations a couple of tac strikes might be used, and between strategic strikes and tac strikes the hope would be the IDF could push Arab armies back past the 1967 prewar borders or beyond. Since the plan would be for Israel to continue, hitting Mecca would be something that would be seen as gratuitous and further inflame international opinion and would piss off Muslims in non-Arab countries who might very well not care much about the "Palestinian cause". Of course, if the Israelis see overrun as inevitable, maybe gas has been used on civilians and so forth, then Mecca becomes a revenge target. I would even go so far as to suggest that hitting Saudi and other oil fields (a ground burst followed by an airburst to blow the fallout back down on the oil field for long term contamination) as a middle finger to the world that stood by (again) in the face of a Jewish Holocaust could happen.
In the "stop the war" Samson option IMHO ground zero for most nukes would be military bases, now if they were next to a city too bad. Damascus, Baghdad, Cairo would be hit with GZ being the defense ministry, and of course bye-bye Aswan Dam. Alexandria and Latakia naval bases go away as examples. In the stop the war scenario the Israelis want to destroy Arab military-industrial capabilities so another attack is a long way off. Once you get to revenge, all bets are off - city busting, Mecca, one one the Suez Canal and so forth. The only country that might get off scot-free in the region is Iran, which in 1973 was still under the Shah and not participating against Israel.