The Pro version of Quick Index has an option to automatically prepend the Headings in the content with the numbers used in the index.

For example, this Index:

  1. Fruit
    1. Apples
    2. Bananas
  2. Animals
    1. Cats
    2. Dogs

...would convert the Headings in the content to:

1. Fruit

Fruit is yummy.

1.1. Apples

Apples are round and delicious.

1.1. Bananas

Bananaaaaas!

2. Animals

Furry animals!

1.1. Cats

Aaah... a cat :)

1.1. Dogs

Sit!