Charging system

First does this truck have external voltage regulator? I installed two junk yard alternators think I have went over checked and cleaned all grounds and connections yet still average 12.11 - 12.86 volts out of alternator testing with red lead on big wire and black on alternator housing. Also got battery voltage out of one small field terminal and a sporadic reading on other small terminal but nothing close to the other side could the regulator be bad or do you think I have ended up with two bad alternator's and two bad batteries? I have noticed the battery loosing some power while sitting but while testing I made sure it was reading 12.6 volts. I would also get the 12.6 out of alternator, but never higher than battery voltage also showing codes 41 and 32. I cleaned EGR and installed another diagram.