The answer to this is as difficult as the meaning life it's self.
But if you pull the Pistons and cylinders off and find that the wrist pins are out of spec in the connecting rod bushing well... You won't be able to live with yourself just putting it all back together. It will knock. then fly apart.
Heads should be lapped to the matting cylinder. If you omit the head gasket you effectively reduce your deck hieght and raise your compression. Damn now you got to measure this and get base cylinder shims if the deck is too short.
What are you going to do to the heads???? You should be able to clean them up enough to see cracks before taking into machinist. you can also do a fluid test to see if the valves seal or not. Getting deeper than that involves pulling the valves then you can asess the valve guide wear. I can already hear the money falling out of your pockets.
Sure good idea to go splunking for rust (which you should have no problem finding. So now that your 914 is going to be setting up on the jackstands for awhile it is official. youre a 914 owner.