Ok, here's some clarification;
The top one is a GT crank (Not to be confused with N1), runs a 77.7mm stroke (eg 2.8L), as you can see its a serious bit of gear.
The bottom is a standard GTR crank, 73.7mm stroke, used in all GTR road cars that are 2.6L (so all normal GTR's, V Specs, V Spec2's, NUR and N1's). Eventhough that particular one is being sold as N1 (and a lot of shops do the same thing here, maybe it boosts sales?!) its just a stock GTR crank. Part number from FAST for an N1 engine lists it as 12200-05U03, part number for a stock standard RB26 in FAST also shows the exact same crank as 12200-05U03.
FYI the majority (if not all) N1 parts have "24U" in the code in place of "05U". Lastly, the GT crank is from Nismo not Nissan.
Good luck with the build.