Somebody correct me if I'm wrong on this.
But the LA motor oils through the number two and number four cam journal to the heads to the passage from the cam to the rocker arm shaft.
The Magnum oils through the lifter from the oil gallery through the push rod to the rocker arm.
So technically you should not have to crank the Magnum motor around in order to oil the rocker arms. Because the oil is coming from the gallery rather than from a hole in the cam journal.
Also isn't it possible to put those roller lifters in backward to where the oil hole on the lifter is pointing away from the gallery.