As most of our freeze plugs are getting on in years (and to be honest we probably have not used the right coolant or done our flushes) I thought I would share my experience.
The 1st picture is the leak from the #2 plug on the Rt side of my 1979 SD (617). I took all stuff out of the way IE: air cleaner, turbo, manifold A search of the net lead me to the conclusion that if one was bad, soon the others would go. So i decided to replace all three. I ordered the part from the dealer and the plug was only $5.00 per. I ordered 4 as I thought I may screw one up( I did not)
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I assembled all the tools, emery cloth,brakleen and Permaflex 2 form-a-gasket.
Clean the area well so as not to get any gunk into the coolant passages when you knock out the old plugs.
I used a 1/2 punch and then a rolling head pry par worked well for the 1st two. Then I ran into a problem- My punch started to pushed the plug into the passage- I solved the problem by screwing a bolt into the plug to keep it from falling into the coolant passage and then I was able to use pliers to deform it and using the bolt to pull it out. Sounds simple but took an hour or so of careful trial and error. Next the installation...