A split lock washer under a main bearing bolt is a really bad idea, as they usually spread out at the split and let the bolt lose its torque. If a washer is used at all, it would need to be a hardened Grade 8 SAE flat washer, never a lock washer of any kind. The head bolt with the slot across the top is one with a 1/16" hole drilled through the center, and another hole at right angles intersecting it above the threaded part of the bolt. It's there to adapt the oil circuit to the rocker arms on certain cylinder head/rocker arm combinations. That bolt is supposed to be located at the center of the head on the passenger's side, and if there's a piece of 3/16" tubing from the pushrod valley to the oil connector in the center of the rocket arms, that bolt isn't needed.
Jerry
