No oil pressure

OK the pump evidently works, did you pre-fill the filter? Maybe you did not give the system time to fill the filter and develop pressure?

WHAT DID YOU DO TO THE ENGINE? Did you have it torn down to bare block? hot tanked? Did you or someone open up the oil passages to clean them? If so, there are a number of plugs, if someone else was involved, that can screw ya up

1...There are plugs in the front oil passages, also normally covered by the cam retainer. That might be an issue

2...At the rear of the engine, inside the bell, are three plugs. ONE of them is a trick. You remove the plug, it provides for ANOTHER plug inside the valley, near the dist. Pull the dist and look down the hole, you can see that plug if it's installed. Plugs the rear of the driver side lifter passage but INSIDE the block.

3..There's a trick plug (I forget is there 2?) in the oil pump / filter passages. One is in the vertical passage with the pump output at the bottom and the gauge port at the top. There is a way to stick a rod down the gauge port, measure it, and determine if that plug is properly seated

4...Some pans interfere with the pump and can force it over enough to break the pump. Keep that in mind

Part of it this thread
https://www.forabodiesonly.com/mopar/threads/340-oil-galley-plugs.377270/
The drive in plug in the vertical passage
https://www.forbbodiesonly.com/moparforum/threads/360-oil-galley-plugs.181611/
Another. Look particularly at the photo in post no. 7

https://www.forabodiesonly.com/mopar/threads/inner-sactum-oil-galley-plug.394594/