lifter galley crossover tube

That mod dates back to the trans am efforts and is for the #4 main, to slow the speed of oil down the pass side oil galley, to help starvation at very high rpm. It has to be done as in the 2nd pic (OP's) so the oil from the drivers valley is utilized for it and the fitting going into the pass side is critical. If you can't do it right, don't bother. The effectiveness of it is always in question. I've never bothered with it myself.

Edit, after blowing the picture up that one is done wrong. A 90* fitting there will negate any positive effect. The mod is for #4 main bearing oil feed and rods 5 & 6 that it feeds iirc.
Nothing more.