N77V or NR77V. There is ONLY one that should be showing up for this number.
Serial # EK-Z1, based in Florida is the correct one. I know the builders Jeff Eicher and Kevin Kimball (the E and K of the serial), they had a hard time getting that tail number because another aircraft at the time was using it. They finally got it to make it official. It is currently owned by Kermit Weeks with Fantasy of Flight Polk City Florida. It is also possibly flyable again as Kermit was testing it a couple years back and may get it airborne, so the reg is still legit. Here is the original flying video of it
https://www.youtube.com/watch?v=og1MHoYY-mc&t=584s
The other GeeBee Z serial # T4 is actually N77VV, this one is located in California. While it shows on display as N77V, it did not fly as that. They put a small V behind the large V.
If the Mods could please update Serial #T4 to show as N77VV, that would be nice