65 Barracuda daily driver

One more thing I noticed that could explain my startup oil pressure issue: I was using a Wix 51515 and before that a STP S8A and after some research I found out that the 51515 doesn't have a standpipe. Don't know about the STP. Both have a anti-drainback valve, which I thought was the same as the standpipe. Anyways, now I got a Wix 51806, which supposedly has the standpipe.