I dont see new rings listed on that build.....thats a concern....
I would be doing a leak down test, but first, run the engine for about 30 minutes to burn off as much cylinder oil as possible...keep the pcv system shut off...
Make sure you check the oil level...
That low oil pressure could be a bad O ring on the pickup tube....
![mmmmm](http://67-72chevytrucks.com/vboard/images/smilies/mmmm.gif)
![mmmmm](http://67-72chevytrucks.com/vboard/images/smilies/mmmm.gif)