Oldtruckin

I think its time to admit defeat on my 5.3 build. I got the motor used, took to machine shop and had it bored .020 over, polished crank, cam bearings and heads done. I assembled it, used plastigage on bearings, rods in spec, main bearings were on the tighter side of tolerance but ok, i dont remember exact number. I put a btr truck cam in. I didnt know it had to be tuned for cam, so it did not get a 20 min break in cause it didnt stay running. I swapped factory cam back in. From day one oil pressure has not been great, around 40 on start up onced up good, around 10 at idle. I have checked with mechanical guage. I have done 3 oil changes so far, cut filters open, no chuncks just some glitter. I swapped in melling high pressure pump and a new oring. Pressure is a 45 accelerating, but still 10 to 15 at idle. Seems to have a slight tapping noise, i unplugged each plug wire to try to isolate it but made no difference. I am assuming main bearing issue, any other thoughts?