Fair point regarding the price difference. Unfortunately i am no engine builder so i can not add anything of value. But one thing to consider is that this engine has worked for 100k miles so they have proved their worth more or less
With these new shells you are adding a unknown variable and if it goes bust it will be very difficult to prove that it was because of the shells. But if they are of better quality while being cheaper than OEM its certainly a tough choice to make.