1995 Toyota 4Runner low oil pressure

I have a 1995 Toyota 4Runner SR5 V6. Last month, on my way back from California I through a rod and destroyed my engine. The next day I ordered a Japanese crate motor that supposedly had between 30 to 60K. After putting the new motor in I have noticed that the motor runs at an extremely low oil pressure and has a slight shudder at about 2,500 RPM's. The motor seemed to have a slight miss, so I changed the plugs and made sure that the wires and distributer were good. The engine seems to run a little better, but I still have low oil pressure and it still doesn't seem to be running right. I hear a minor tick coming from below the motor on the drivers side which did not seem to be there before. I have disconnected the EGR, however the problem continues whether it is connected or not. Could the tick that I hear be a bad rocker arm, and if so would that effect the oil pressure? I have a six month warranty on the engine and need to figure out how severe this problem is before the six months is up so I can get a replacement if it is needed. Any feedback would be greatly appreciated. Thanks, Sam