Hello @Poley ,
MBDT for S32K3 works in a different way than the MBDT for S32K1 works. The MBDT for S32K3 is based on the Real-Time Drivers and generates the configuration codes for the MCU using external configuration tools and not using the configuration blocks as the S32K1. This is why, on each of the MBDT blocks for the K3, you will find the Configure and the Refresh Button. Pressing the Configure button, opens the external configuration tools, like the EBTresos or S32 Configuration tools, allowing to assign pins and configure peripherals while pressing the Refresh button reads the settings from the configuration tools and updates the options inside dropdowns of the blocks.

From the options on top, and also my explanations, you could see that there is a strong bond between the MBDT and the RTD. Coming back to your question, the MBDT only supports the MC33775A for battery cell controllers and the MC33772C (which is the HVBMS this is used only as a current measurement for the Battery Junction Box). In other words, the BMS drivers support only MC33775A and the MC33772C therefore the MC33771C is not supported, MC33775A being its replacement. Unfortunately, the Simulink blocks could not be used across Toolboxes, so the blocks from the MBDT for S32K1xx could not be used for the MBDT for S32K3xx.
For the loopback, on the HVBMS there is used the newer MC33665, is the replacement for the MC33664, and this has 4 ports for the TPL, therefore you don't need to use 2xMC33664 for loopback, 1xMC33665 will be just fine to address also the loopback.
Regards,
Marius