Other than the concept of (yeeeugh), I don't think there are many official mentions of Centaurs in Blackmoor material?

I could see many of them living among the Peshwa or otherwise roaming the Plains of Hak.

I think many of the PrCs found in Sons of Hak can be adapted to Centaur roles regardless of your preferred edition.

I also think the Sprit Warrior concept form DABd20 and Spirit Animals is something that fits well with Centaurs.

Also, there are Dragon Knights.

Or you could take the Fey/Sylvan route and make them Fey lords, Rangers etc. Connect them to other Fey races, elves and so on.

-Havard

You could take a route similar to Allansia
https://fightingfantasy.fandom.com/wiki/Centaur