Exhaust/valve guide position (They alternate)
Replace water distribution tube
Make sure the timing chain oiler tube is installed
Rods are offset, make sure the order is correct.
Make sure the block is fully flushed with all freeze plugs pulled (including the ones at the back of the block)
Replace the cam bearings
Make sure cam/oil pump is installed correctly so timing is correct.
Don't trim the oil pan gaskets
Don't forget to install the rubber gaskets at the front and rear mains.
Distributor has a gasket going into the block (Sometimes an "O" ring is used)
Make sure the oil pressure relief valve is installed correct and works correctly.
Pre pressurize the oil system before before first start (Assembly lube is gone after 1 or 2 revolutions.)
Replace valve seats as needed, exhaust seats are hardened.
Triple grind valves, no lapping needed.
If front crankshaft hub sealing surface is worn, speed-sleeve it so it won't leak.