We've been using the OSK brand timing kits since day 1. High quality, Japanese made kits.
Unlike a timing belt, there is no recommend time or mileage specified by the manufacturer for replacement. Over the years and piles of miles, timing chains stretch, gears wear, tensioners get weak and worn. Ignore them long enough and you'll risk some internal badness. That's how you end up with a broken guide rail and worse.
Our kit includes the new chain, tensioner, both timing gears, guides (including the steel guide rail on the drivers side), timing cover gaskets and a front oil pump seal.