without disassembly is there a way to tell which crankshaft is in the motor?

 

Look at the crank angle sensor, pass side near the starter. 24x is black. 58x is light gray

 

You won't find a 28 or 56 used in the LS engine's.

Its either 24X or 58X and the color of the crank sensor well tell you as mentioned above by Darth V8r

 

Newer 58x sensors can also be black. I just got one that's for 58x and it's black. Acdelco too

 

To actually tell what crank is in the engine...........look at the reluctor wheel..

If the engine has the correct crank sensor in it, then yes go off color. But what if some idiot through the wrong crank sensor in it?

The 58x wheel is one piece and solid. The 24x wheel looks like several pieces of metal that are stacked on top of each other like a samwich

 

If it's out of the car, pull the pan and count the teeth.

 

Counting.....LOL!

Just look at the teeth and you'll know.

 

Ahh I think it would probably just be easier to look at the wheel....58x on the left, 24x on the right.

 

A factory 58x reluctor wheel will be in a Gen IV engine, so you should also see cam sensor located on the front cover, and knock sensors on the side of the engine block (close to engine mounts).

But presence of cam sensor in front cover doesn't guarantee anything because most aftermarket cams are 3-bolt style, so if the engine had a cam swap then it might also have front cover with cam sensor.