Although I personally wouldn't want to set it up this way...
Is it possible to have one indexer that works for 2 separate search heads with 2 separate knowledge bundles? Wouldn't that cause a problem?
If you want both search head to use the common set of knowledge bundle, you need to configure Search head pooling.
It is possible! However, any extractions that you want from one to the other need manually transferred. The data would be indexed in exactly the same way, but any Apps or search time modifications would be different.
Thanks so much!