Fickle means that they have a greater chance of developing leaks. Fickle means that there are warm-up and operating guidelines that are a little more strict because of bearing clearance.
A Shelby block is stronger than an original FE block. Not stronger than an aftermarket cast iron block. You do have reduced ring seal from the aluminum block just because things move around so much.
We're not driving Porsches.
Thanks for the 11 pages of backing-and-forthing. I feel better.