There is no formal 'Differernces Training' requirement for nose wheel undercarriage or fixed pitch props. That's not to say that it wouldn't be a good idea to get someone to cover how they differ and what to do about, just that they are not things listed in the Regulations as requiring Differences Training.
I'd get your instructor to anotate your log-book to say you are trained to fly tailwheel, VP prop and retractable u/c. There is no actual need but it might stop an argument/discussion where none is needed in the future.
Belt/braces...