There are certain nouns in English that are plural only and have no singular equivalents. Some such as trousers, scissors, pajamas, pantyhose, shears, binoculars, headphones, etc. can be singularized with pair or set, which could mean that many could be grammatically placed before them.
I have many pairs of trousers.
But not all nouns are like these. Take clothes, goods, thanks, shenanigans, antics for example. While there seem to be quite many citations on Google Books for many clothes, many goods, many thanks, many shenanigans, many antics:
And then I do what any self-respecting New York woman with too many books and too many clothes does when she's frustrated. (So Many Books, So Little Time: A Year of Passionate Reading by Sara Nelson)
An IPC is a broad classification that contains many goods or services. (How Many Trademarks Does it Take to Protect a Brand?: The Optimal Number of Trademarks, Branding Strategy and Brand Performance by Mary Sullivan)
Walter's attraction to Hildy was clear through his many antics to regain her affection both during and after their divorce. (Classical Hollywood Comedy by Alan Jenkins)
I'm still not 100% confident that many can be used like this. Is there an authoritative source on how to deal with specifically many and pluralia tantum?