Just replaced oil pump and oil pressure wont go.

The pump may not have been the issue. It may be worn main and/or rod bearings causing low oil pressure.

Roy

At 2K rpm the oil pressure should be around 40psi-sounds more like excessive bearing clearances as mentioned earlier, to rule it out you need a plastigauge/micrometer and measure the clearance-if excessive either you have it ground and use undersized bearings or just get a crankshaft kit-