R33 GTR N1
Still a RB26DETT but the water cooling channels in the block are enhanced to increase flow.
The block and internal components are strengthened.
The pistons have 1.2 mm (0.047 in) top rings, but otherwise as standard.
The connecting rods are standard.
The crankshaft is standard but balanced / refined.
The specifications of the camshafts were improved for power.
Upgraded oil and water pump, to improve the cooling and lubrication of the engine.
Larger and stronger twin turbo's.
Nismo 400R
Used a RB26DETT but is modified and stroked to a 2.8lt.
From memory, it is built at the Nismo Omori Factory.
Reinforced cylinder block / cylinder head / metal head gasket / pistons with cooling channels.
Forged crank shaft / connecting rods.
N1 turbines with reinforced actuator.
High flow air intake.
Upgraded exhaust system.
The Nismo 400R is the only car that Nismo built from Factory with a 2.8lt.
Having said that, Nissan / Nismo never made a RB28DETT from factory as they are all RB26DETT's but Stroked to a 2.8lt, in my opinion.
The rest were 2.6lt, but if you have the import papers to let us have a look then I would be interested to see.