Do you also have a question about raw hearts and gizzards?
The USDA food database is a great source of information.
https://ndb.nal.usda.gov/ndb/search/list
Where it says Enter one or more terms (For example: raw broccoli box) type the food you want to look up. In your case raw chicken gizzards or raw chicken hearts. (I'm assuming you meant chicken.)
Scroll through the list until you find what you are looking for - in this case chicken, heart, all classes, raw. Click on it.
When the page comes up, click on Full report (All nutrients).
Some of the items give you a 1 oz column. Some don't so you can just do the math from the 100g. 100g = 3.527 oz
Chicken gizzards 100g has Phosphorus 148mg, Sodium 69mg
Chicken hearts 100g has Phosphorus 177mg, Sodium 74mg
Those are just two nutrients you might care about for example a cat with any kidney insufficiency (phosphorous). Another might be the fat content for those with a history of pancreatitis. Knowing the nutrients lets you tailor what you choose for each individual cat.
As far as using one or the other or other meat, it's a great idea. This is the ingredient list for Greenies Pill Pockets for cats:
Rehydrated Chicken, Glycerin, Wheat Flour, Wheat Gluten, Hydrolyzed Salmon (Source of Salmon Flavor), Vegetable Oil, Natural Flavors, Dried Corn Syrup, Dried Cultured Skim Milk, Sodium Bisulfate, Xanthan Gum, Preserved with Mixed Tocopherols.