Hello @ranulf ,
The MPC57xx v 3.2.0 supports the MPC5748G controller so I see no reason why it wouldn't work on the mentioned DEVKIT. When the support was added, we've tested the functionalities on the DEVKIT-MPC5748G revision B, the revision we had at that time.
I see no reason why it shouldn't work with the DEVIT-COMM board, this board uses the TJA1048, a dual CAN transceiver with no SPI connection, so no additional driver is needed. All you have to do is to check the schematics of both boards in order to assign the correct CANRX and CANTX pins for the DEVKIT with the COMM board on desired instances.
To program the board directly from Simulink, you have to use the RAppID bootloader. MBDT comes with the required RBF file for the MPC5748G which has to be flashed using the S32DS for Power Architecture. The procedure is similar to the one used for the MPC5777C except that for the MPC5748G there is no need to use an Alternative Algorithm selection in S32DS for flashing the RBF file.
Hope this helps,
Marius