Do you have the oil pump drive shaft installed?
Did you ever have oil pressure?
If so, check pressure with a manual gauge. If not, then it must be shaft related or the pump.

 

SBC chevys have great stock oiling. even with a 383 setup i have a stock replacement was suggested. when i told the guy how many miles were on the car he hinted that i shouldnt even replace it. if you dont think it's adequate i was watching one of the shows on SPIKE this weekend where they rebuild cars and test them and all kinds of stuff...they had a 396 with a deep sump oil pan and used a stock pump with a longer driveshaft...that's it, making over 550 hp.

i have over 450 hp and am using a stock unit, new of course when rebuilt.

 

From Build Its Not Had Oil Pressure And I Have Used The Cauge In The Dash Which Worked Well Before The Build And A Aftermarket Gauge From Autozone ...yes The Shaft Is In It It Has No Oil Pressure At An Idle But When You Rev It Up I Gats About 25 Psi oops sorry about the caps

 

Do you trust the person who built your motor? Might be a bearing problems. What kind of pump do you have?

 

Maybe the pickup is too low and it is choking the pump. I have a feeling you might be pulling the motor back out. You don't want to tear anything up running it and running it trying to find the source of this problem. Did the engine builder prime the pump? Did he say everything looked ok when he did?

 

I'd pull it back out and get it figured out.