Best thing imo is keep this one and just abandon the other thread.
disconnect power to the fuel solenoid and the glow plug controller connector(leave the 8 big wires is ok). Pull all 8 of the plugs first, then crank a few revolutions with the compression tester to make sure no water is coming out of the holes.
Make sure it is a diesel compression tester not gasoline engine one. Our much higher compression can’t be read on the low 300psi pressure gasoline gauge. Most diesel testers have a gauge to 1,000 psi. For this engine I prefer the gauge that goes to 600 psi because you can get a more accurate reading ( not required though) The digital ones are nice because they are exact- but are a lot more money and often not rented out. A really healthy stock 6.5 is around 400 psi. Crank at least 5 revolutions each time to peak the reading. Write down each as you go. Remember cylinders are numbered front to back -driver side 1,3,5,7 passenger side 2,4,6,8.
If local parts stores don’t have the ‘free rental’ then amazon, harbor freight, etc. if you we’re doing it all the time a pro tool is better but if you only do a few engines with it the cheaper ones are fine.
A request- when typing a lot throw in a space every few sentences, Many of us are on phones, and it helps follow easier.