Hi,
I'm afraid IAR Embedded Workbench v6.x plugin is not supported/tested by S32DS project wizard.
The supported/tested versions of IAR eclipse plugins are v7.x and v8.11.x. (see S32 Design Studio for ARM 2018.R1 (Windows/Linux) released! )


Installing 78K plug-in target has no influence on the S32DS (new project wizard) at all.
IAR eclipse plugin does not generate any makefile. The tool-chain exe (iccarm, ilinkarm,...) are called internally by the plugin - the makefile is not generated at all (see the screenshot with grayed makefile generation options).

Anyway I'd recommend you to contact IAR support regarding the compatibility across different versions + if there is any way to generate makefile since both eclipse plugin and tool-chain are developed by IAR.
Hope it helps.
Stan