The US Navy decided not to upgrade the FFG-7s with SeaRam due to the ship's age when they removed the Mk 13 SM-1MR launchers. I would assume Pakistan would include the SeaRam as they will be using the frigates for a longer time, making the investment worthwhile...
I doubt seriously the US Navy would reinstall the Mk 13 launcher and the STIP sensor, but I maybe mistaken... Eventually, there will be an inventory or shortage problem with the standard missiles...
Frankly, I would install the SeaRams instead... That would provide eleven rolling airframe missiles for CIWS using the Mk 15 20-mm Vulcan Phalanx CIWS mount and sensors... And I would use racks for eight harpoons in front of the bridge...
Doing so wouldn't involve spending as much as the Australians to upgrade with ESSMs and the Mk 41 VLS... In other words do the upgrade the Americans were thinking of doing but didn't... Such an upgraded Perry class frigate would be a better value than the previous Nato Seasparrow equipped Knox class frigates seen in Mexico, Taiwan and Turkey...