414 block half fill in waterjackets

Probably a reason for that...lol.
Filling to the bottom of the freeze plugs does very little to support the walls - especially where they would need it - the top 1/2 of the bore. That's what a mopar small block needs and what fill was designed to be used for. It can help on big blocks to add strenght to the webbing - but smallblocks don't need that. A low level fill simply takes away a lot of surface area where heat is transferred out of the oil.