Hi Jeff,
Sorry for late.
I have just found this thread.
NUR engine is based on N1 engine block, so the strength is definitly better than the standard engine.
More than a half of standard RB26DETT blocks have been broken when we tested the 500ps engine based on standard RB26DETT engine on the engine bench.
N1 engine has thicker rib than standard one, so it is much stronger than the standard block.
If you'd like to go for more than 440ps, at least you should change air flow meters, injectors and fuel pumps.
The factory air flow meters and injecotrs are applicable up to around 440ps, and when you change the injecotrs, you need big capacity fuel pump as well.
Further, when you use more than 1.2 bar boost pressure, you should change head gasket.
The difference between standard RB26DETT and N1 RB26DETT is thicker ribs, pistons, piston rings, con-rods, smoother exhaust manifold, etc.
And the difference between N1 engine and NUR engine is basically the same, but the big difference is the weight balance of piston and con-rods.
Nissan uses the +-1g balanced pistons and con-rods for NUR engine, so NUR engine is much smoother than the standard N1 engine.
By the way, the initial RB26DETT for GTR32 used to use N1 block, but because of the cost, the engine block got thinner.
Finally, there are generally three type of engines.
1) NUR RB26DETT
2) N1 RB26DETT
3) GTR34 RB26DETT
4) GTR32/GTR33 RB26DETT
The major difference between 3) and 4) is con-rod bearing.
3) uses N1 con-rod bearing.
Yours,
Shin