Back in the day, piston rings were a big one. Old cast rings versus moly rings, the difference is huge. Even in the late 318's and magnum engines, cylinder bore wear is night and day versus the old ones.

Also, fuel management. If you've ever cracked the head off a carbed engine compared to the same engine with port EFI, the pistons and valves on the fuel injected one are very clean. On the carbed one they are all junked and carboned up. All that raw fuel, running rich, poor fuel distribution, takes it's toll on engines.