68 with original 327. My harmonic balancer was a pressfit one and it worked itself off. The Key slot on the crankshaft is way wider then it should be because of this. I haven't measured the crankshaft to see if it got worn away too.
My question is has anyone ever just replaced a crankshaft without taking apart the whole engine top? I am hoping to pull the engine out of the car, turn it upside-down and remove the crankshaft. not taking out pistons or valves or anything on the top half of the engine. The engine was rebuilt just 5 thousand miles ago. (yes its my fault i must not have gotten the balancer on right).
What problems will I have if I do this?

 

If you're pulling it, then it's pretty easy to do. You don't have to pull the top end. Just make sure you're stand can take the extra weight (most should). Check over the main and rod bearings but with only 5k miles, should be good to go. Wouldn't hurt check the clearances though. If alls good, replace crank, all bottom end gaskets, press on new balancer, and reinstall in car.

 

You might check the snout in seeing if it is threaded and if it is, add a key, install balancer, and balancer bolt with washer and antiseize on threads after cleaning crank threads.
Hopefully, your 327 is not a 210HP (2-bbl) as they were not threaded.