To anyone considering implementing this as a diet, a word of caution:
When eating a whole prey item or something like the snake sausages, remember that it's not just protein, fat, and bone (calcium) that the snakes are getting. The majority of a carnivore's vitamin and micronutrient requirement is filled by eating the gut contents...something you will not get from turkey necks or boiled pork. They also get the diet of the prey item which is typically loaded with carbs. Your snake may not die in a year or two, but over time the lack of vitamins and micronutrients will have it's toll.
There is nothing wrong with feeding pieces of meat, boiled or no. The snake can digest it. It's not harmful. Keep in mind, though, that you need to get your vitamins and micronutrients from somewhere...and they aren't in the muscle and bone of any animal. Those parts with the fat around them supply energy, protein, and calcium, but very little else. Also keep in mind that you are no longer feeding them their protein/calcium/fat/carbs in the ratio they are used to. Calcium imbalances are especially deleterious in reptiles, so just think your plan through. A little research never hurt anyone. Don't accept anything anyone says at face value (my advice included), or you have no one to blame but yourself when problems crop up.
Just some thoughts on the subject.
Addendum: A special word of caution regarding liver...very very high in vitamin A. Hypervitaminosis A (too much Vitamin A in the diet) will lead to excessive bone production and fusion of the spine. A little liver won't hurt you, but a diet of liver is toxic.