The line to the front only feeds the #1 main. I'm using a -6AN which is a 3/8" feed...plenty if you ask me.
You only need one line and a sandwich adaptor....easy.
The feed line crossing from the right oil gallery to the left only supplies oil to the lifters on that side...not really needed if running solid lifters.
Your R3 block shouldn't need any extra oil to the front IIRC...that was fixed by Mopar.