I have loads of minifigures from the 1980's and have just found out that none of the arms or individual legs are stamped with the LEGO logo.However, torsos, heads, and hips are all stamped. Does this mean they are not genuine parts?
Torsos and leg-pieces are special. They are some of the few pieces of their size that are not actually two separate parts of different IDs. Torsos actually include their two arms, which is why they come assembled, with the arms and hands already attached, and only the torso is stamped. Legs are actually a three-piece combo of left, right, and waist. A mini-figure is made of (typically) a hat/hair piece, a head, a torso-combo, and a leg-combo, all of which have only one stamp apiece. So fortunately for you...
All of your pieces are legitimate.