99 dakota V-6 3.9 135k miles

This has been troubling me.. for no apparent reason, the engine in my 99 dakota 3.9 started this noise. It happens when the truck is warmed up, in drive and in reverse. I can barely hear it when in park. It is loud enough that it echos off of other cars in traffic. Clunk Clunk Clunk noise coming from the front lower part of the engine. It is very noticeable when sitting at idle. It becomes loud at 1000 and 2000 rpms and after that you can not hear it as much. It almost sounds like metal on metal coming from an internal part of the engine.

I just replaced the rod and main bearings as well as the oil pump. While I had it apart I checked for play in the wrist pins and found none. However I did find enough play in the pistons that they would shift slightly back and forth. I don't know these engines well so I am not sure how much play they are supposed to have.

After the engine was back together I notice the noise was much quieter, but it is slowly starting to grow louder again. Especially between 2k-3k rpm. I also noticed that I have around 80 pounds of oil pressure on a cold start and while the engine is warming up it drops to about 35 pounds every time i stop or let off the gas. Eventually when the motor is at reg. temperature it stays at 35 pounds.
When the engine is cold there is no clunking noise. I dont know if it is caused by thermal expansion or low oil pressure.

Has anyone had these problems, and does anyone have any solutions?

i'm not sure about the noise you're describing, but the spec for engine oil pressure (at operating temp) is about 8 psi at an idle (min.) and up, thats straight out of the dealer service manual, so i cant see that being yoiur issue