Sorry, but that's also known . All makes of blocks are imported here, so if one is perceived as being more desirable than the other, then that's what importers try to source. HD, Truck, cold weather, etc, from whatever brand.
The guy I used to get import parts from would blab about it to everyone interested in getting blocks and everyone likes to be "in the know" so it just spread from there. The Mopar community is small here, so everything spreads fast.
I think the next secret should be stroked 361 blocks..