The first is the long draw bolt affair at the back of the head. Unless it's been adjusted in the recent past, keep your torch handy, and when loose use lots of never seize on the threads.
The second is the rod and ball joints that attach the arms to the skid pads. Take all your feather sheets off, blow/scrape off all the crap that's built up around the ball joints....heck just all the crap under the feather sheets, wire brush the threaded rods and any swivel areas, and spray/coat everything with penetrating oil. Walk away for a day or so. When you come back, make sure you've got your torch handy and loosen/remove the lock nuts and bolts that hold the arms to the pads so you can move the threaded rods in or out to get the knife to pitch up or down as you desire. This is really the fine adjustment for your knife, and you may only have to do this if you can't get the rear adjustment to go as far as you want.
Aside from the distance from the knife to the table conveyor, this is the worst feature on a 300 head. The area under the feather sheets and between the knife bar and the pads is difficult to keep clean, so all sorts of corruption gets up in there causing the moving parts and adjustment areas to rust up. Never seize is your friend!