Max,
I don't think there is a special tool for that.
By the way, 53 and probably 63FZ don't have separate liners, the head and liner are in one piece. (Costs a lot!).

4-stroke liner should not be hard to replace since there is no hole on the wall of the liner. Maybe there is a notch just for direction. No idea on that.

Try to pull the outside skirt of the liner from the head. if it doesn't come out I would use a thin blade between the head and liner skirt very carefully.

I have no idea of torque settings on cap-screws. I always tighten them until it is just tight enough. Well, that's kind hard to explain. I would go no more than 1/2 turn after hand tightening and retighten after a shor run.

Sorry, I can't be any more help on this.

Dave,
I don't know why there are two different crankcase and cylinder heads. Central hobbies still have same part numbers for both 91 AC & FZ.

If they are different aren't they supporsed to have different part numbers?