Oil pump priming question

I have a 71 Duster I just dropped the 340 LA engine back into. Went to prime the oil pump/engine with the hex head tool and drill. After 4 to 5 minutes of priming the oil gauge only read about 5 -10 psi. I took the oil gauge off and blew compressed air into it and the gauge moved to about 20-25 psi. Then I primed the engine with the oil gauge of to see if oil was coming out and just a drop every now and then. When I took the copper gauge line out at the block and primed it, tons of oil cam gushing out. So I know lots of oil is getting to the start of the oil gauge line just not going through it. So I bought a new copper gauge oil line. installed it and made sure I didn't kink it. Same thing when I prime the engine I get lots of oil to the start of the copper line but just little drops of oil to the oil gauge and the gauge only reads 5-10 psi. Also have not seen oil get to the rocker arms yet. priming clockwise and turned the engine over slow clockwise. Is there something I am missing? Do I just need to prime it longer? I have primed it for about 6-8 minutes. so much that my drill starts to heat up really hot so I stop to let it cool down. Other have said it take a couple of minutes, so I feel like it should be showing oil pressure at least by now. Thank in advance for any help.