The oil pressure switch at back of block...how many wires are on it?
Seems it may be a faulty factory sender unit....
I am wondering whether the cam bearings were actually changed or not...this could also be some bad lifters....wondering why the build lists new lifters....
Exactly where the old school switch is screwed into the block...
I am attaching an oil flow pic of the LS systems...fail points in the system are the pickup O ring into the pump feed, bad pump, bad lifter clearances and bad cam bearing clearances...and finally, bad main bearing clearances.
There is also a "dumbell" plug in the rear oil gallery drivers side that forms part of the oil flow system....I have seen engines without these in place...effectively bypassing any filter function.....here is a youtube video showing the valve
https://www.youtube.com/watch?v=4Hi9XMQ1S_4