Doesn't seem to be any sites that list in detail what items require what junk. What's more, items require junk from different classes, re Legendary items require both Rare and Legendary Junk to craft...but the game never tells you what junk they are, as some junk have identical icons as others but with different background, of which do not appear in the crafting list.

Besides a list, a very simple solution would solve this: in the list of crafting items, the ingredients have their respective background colours- green for common, blue for rare and orange for legendary.