After poking around a bit, I did find CLOCK_SetMcgliteConfig(), and that does the job. However, I am still surprised the API reference document for the SDK refers to a function, CLOCK_SetInternalRefClkConfig() that apparently does not exist.
Also, I believe there is an issue in CLOCK_SetMcgliteConfig(), in the following line of code:
MCG->C1 = MCG_C1_CLKS(targetConfig->outSrc) | targetConfig->irclkEnableMode;
If irclkEnableMode is just a 0 or a 1, then the C1 bit this is loaded into is incorrect...it needs to be shifted into bit 1.
Thanks,
Chuck