Hello @Stephen Keating ,
I would suggest to post your question in GoDaddy forums, as the community there may have a wider experience with the specifics of the migrations.
Otherwise, I would not recommend to move internal DNS CNAMES to a public provider unless necessary, for matters of security. There other providers for DNS management in Cloud that can provide you the Public/Internal differentiation. Maybe I am outdated but last time I check GD was not providing that differentiation.
Best regards,
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