350Cs were available with headed masterpins and snap-rings but I don't think very common. The headed pin for a C is T19006 and snap ring A378R.
If the dimpled unheaded pins have never been out before - you need two guys (or big girls I guess) - and sometimes even three is better. One guy holds some sort of big weight behind the master chain link. Another guy on the other side holds a big pin just a bit smaller OD then the master-pin - often with a big handle welded to it so the holder does not have to stand too close. The third guy swings a big sledge. Took many new pins out of new 350Cs that way. As they get older, they get easier -except when they've been welding in with some 7018.
No need to split the track just to change the track adjuster. It easily comes in an out just by unbolting it from the front idler yoke.