So what's the deal with spark plug washers?

The deal with the washers depends on which head you have. And all slant heads will fit any block, so you have to check - lots gets changed over time. If you have drool-tube heads (the plugs go INSIDE the head, in a tube) you need to remove the washers. If it's a peanut head (the plugs screw into the outside of the head and are visible) you leave the washers intact. If you need to take the washers off for a drool-tube head, grab them with a pair of needle nose pliers and twist them till they break. Easy Peasy.