These archives often contain scanned or Parts Lists for the Austin Healey 3000 Mk III. BJ8 Restoration: Part 1 The Teardown

If you are looking for a "piece" in terms of physical components or technical documentation:

They have a well-documented BJ8 Restoration: Part 1 The Teardown which covers the removal of fenders, doors, and the dash pad.

Retailers like Moss Motors offer "full pieces" for the BJ8 interior, such as complete blue vinyl panel kits that include door panels, kick panels, and dash top vinyl.