Low or no oil pressure on new engine, wtf now...

I rebuilt my 340 was back in 98. While I did the body work and interior. We broke the motor in, had some issues with the guides bending push rods, fixed the issues, fast forward to late 2007, the cam (Crane) and lifter go flat. From the time I built the motor until now, it has about 8 miles (NOT in 1/4 mile increments) on the engine and some idle time. Yesterday, we broke in a new cam, Lunati VooDoo. Everything went well, had a few rocker a bit loose but no biggie.

One issue, low oil pressure.

I haven't replaced the gauge (mechanical) but at 800 rpm idle I could pull the line from the sender and get a trickle of oil. Plugged in, gauge showed 0 psi hot idle and about 20 psi at 2000 rpms. Prior to the cam I had good oil pressure. When we had the motor apart for the cam replacement, we checked all the main bearings, they looked fine. At the time of the new cam we did the following new.

Lunati cam and lifters
Hughes timing chain
Mopar timing chain tensioner
Melling HV oil pump
new gaskets

Break in consisted of fresh Valvoline 10/30w and fresh Perolator Gold filter.

Could I have a bad oil pump? Is there something about the timing chain tensioner?

PROGRESS Update

Confirmed:

-the plug by the distributor is there
-gauge is good
-Drive shaft gear on pump drive shaft is good.

Looking at in this order:

-oil pump
-#5 main oil plug