You need to install the camshaft thrust plate, the camshaft thrust plate screws, the
Timing Chain dampener, and the bolts to the block and the crankshaft sprocket, apply engine oil supplement (EOS) GM P/N 1052367 (Canadian P/N 992869) or the equivalent to the sprocket thrust surface, hold the camshaft sprocket with the chain hanging down, and install the chain to the crankshaft gear, align the crankshaft timing mark to the timing mark on the bottom of the timing chain dampener, hold the camshaft sprocket with the timing chain hanging down and install the timing chain to the crankshaft gear, align the timing mark on the camshaft gear with the timing mark on top of the timing chain dampener, install the camshaft sprocket bolt, coat the crankshaft and the camshaft sprocket with engine oil and install the engine front cover.