70 318 with 340 internals/Cyl Head

toolmanmike said

I wouldn't trust the balancer myself. Who knows what combination of parts have been thrown together to make the engine work. And really, who cares. If it runs good and doesn't shake the car apart, run it till it blows or take it apart and check all the pieces.

Click to expand...

Yeah it could have a 340 crank in there and be externally balanced I think that is possible.
And yeah I would not sweat what is inside that engine cause you won't know unless you take it apart.

If engine runs good then look at other aspects of the car I would not focus too much on that engine that is easy to change later.