Would an 94 LT1 be a internal or externally balanced engine?
Sounds dumb but I need to use a externally ballanced flywheel on my t56 swap.
The wheel that came from the donor car has ballance marks but not sure if that is just to ballance the wheel or the motor?

 

The LT1 is externally balanced at the rear as it came from the factory. The harmonic balancer (dampener) is neutral, AFAIK.

Rich

 

Like Rich said - internal on the front, external on the rear.

These motors are balanced with the flywheel in place, but corrections should not be made by drilling on it. I am sure those are factory drill marks to set the balance on the flywheel but it's always best get the replacement part spun up to confirm that it matches the original.