Depends on what's in it. My former '69 Z/28-RS had a real DZ engine not dated to the car, sold it years ago. It hammered at Russo-Steele 2012 for $50,000. I happened to be there and a couple of bidders passed when they learned it was NOM. But still did ok all things considered.
If you don't have the OE engine find one dated for the car and I think you will be ok. Anything else like an LT1 or some crate engine will hurt both value and salability.