Is is "the 80s AD" or "the AD 80s"?

I edit papers on ancient history, and one issue that keeps coming up is whether to refer to "the AD 80s" (or 50s or 90s etc, referring to a decade in the first century AD) or "the 80s AD".

New Hart’s Rules simply states (p. 191):

AD […] should be placed before the numerals, as in AD 375 (not 375 AD). However, when the date is spelled out it is normal to write the third century AD rather than AD the third century.

However, it has no guidance on decades.

Google Ngrams seems to indicate a preference for writing AD before the decade, but when it comes to phrases such as "the early 80s AD [or AD 80s]" there is very little data, and what there is seems to lean toward writing AD after the decade.

House style dictates the use of AD and BC, so I can’t solve it by using CE instead.

So to summarize, how should the following phrases be written (bearing in mind they both occur in the same document, so need to be consistent)?

• the 80s AD, or the AD 80s?
• the early 90s AD, or the early AD 90s?

Many thanks.