Before removing the distributor, put the engine in #1 on TDC. Mark everything, then pull the distributor. When installing, keep in mine that as the distributor sets into place, it will turn, so you have to allow for this. So you wont put it pointing at #1, you will put it about a 1/2 a rotation off. That way, it will be pointing rite at #1 once its stabbed. There are a ton of videos on this on you tube. Watch some and you will see what I am talking about. Also the 4.3L is a 350 or 5.7L just without 2 cylinders ( for the most part) so the procedures are the same. I never pull a valve cover to find #1 TDC. I pull #1 spark plug, have my wife bump spin the starter, after I remove the coil wire so the truck wont start. Them put my thumb over the spark hole as she spins the engine over with the starter. I also watch for the timing marks to line up on the harmonic balancer, and the timing marks on the timing chain cover. There is no mistaking the compression stroke for the exhaust stroke with you thumb over the hole and someone else using the starter to spin the engine over.