This Answer Record describes how to migrate from v7.2 to v7.3 of the SPI-4.2 Core.
There are no pin-out differences between v7.2 and v7.3 Core.
It is possible to drop in v7.3 Core in place of v7.2 Core. However, you must use the new UCF file generated with the v7.3 Core.
For more information on the changes to v7.3 Core, see (Xilinx Answer 21918).