Why is the one on the left different than the stock one on the right?Left is new Mopar Perf.Thanks for any replies.

The open passage from the left hole (in pic) directs additional oil to the timing chain.

I would think with the front of the horizontle galleries being plugged with mini freeze plugs that the change is only a different MFR process cuz there ain't no oil coming out of there that could dribble down but I will defer to John on this.

Don't use the one on the left without the little plug in the galley. You will be down 20 psi oil pressure. I have seen this twice in engines I have freshened that someone else built.

John Kunkel I believe is correct, there should be zero pressure at that opening, the oil is just partially draining the lifter valley.

I had to hunt for oil pressure problems on a motor and they used the plate on the left. It had very poor oil pressure. Don’t use it unless you plug the galley with drive in plug. Stock plates used a bolt with a small hole in it to oil the chain through the lifter valley.

I would always use the mini cup plugs in the (2) horizontle galleries & I drill a 3/8 hole in the pass retainer plate & drill/tap the front of that sides' horizontle gallery for a blue aluminum pipe plug with a .015" hole in it on that side instead of the mini cup plug for a constant mini squirt past the plate onto the chain. But people have said that there is enough slosh in that area that the chain ain't hurtin for oil.

Some small blocks just had the bolt with the hole in it for oiling. Others just had the drip tab. I put both on my last build.

Yes & it is an 1/8" hole that you can easily drill in a regular bolt (& use the drip tray if you have one). EDIT & this is the top pass bolt, the other top one is a blind hole, the two bottom ones go into the valley (if there would be enough splash back there to warrant drilling the bottom ones (couldn't hurt/easy to do).