Ok, I'm at a loss here and need to pick somebody's brain.

I have a 2004 G35 Sedan, 240k miles. the engine was destroyed thanks to the previous owner('s "mechanic") not bolting any of the internals back together. Don't ask me how it wasn't making noise, but a rod and piston welded to the cylinder wall. It wasn't overheating before the engine swap. Now with the new engine in it is overheating. The thermostat was off brand, so I put in a Nissan one. The mechanical fan clutch was messed up during the swap, so I replaced that. The AC condenser fan wasn't blowing hard, so I replaced that motor. All the hoses are 1-3 month old Z1 hoses. I cleaned the outside of the radiator and condenser. I have ran the bleeding procedure a hundred times with the car jacked up and a no spill funnel; get to operating temps, rev to 2500 for 10 seconds, rest, repeat. It has no smoke ( slight white smoke on start up, probably from the motor sitting), no exhaust smell in the coolant, no oil or water mixing.

Before installing the new engine we replaced the full timing set and water pump.

Parked at idle I can see the thermostat open at around 177 - 180 ( watching the temps on TorquePro), parked it will stay under 200 unless I rev it a lot. Once I start driving the temps stay around 200, until I simulate traffic( I do a loop around my neighborhood stopping for a few minutes at each stop sign) then it starts to slowly climb until it gets over 225 or 230. It will go down to 200ish once I get to 60MPH, but jumps right back up when I slow down.

Known issues; the power steering is out and still connected, hoping to get a new line soon, and the knock sensor/ harness are throwing low voltage codes

 

I'd get the engine block test from AutoZone it's like 20 bucks. You stick it on the radiator and the fluid changes color if it detects exhaust gases in your coolant.

I would also make sure the engine coolant sensor is reading correctly. I would check the temp with Torque, cluster, and maybe even a infrared gun. I had a Audi that did some weird **** with the temps and it ended up being a faulty ECT. I'd even look up the FSM for the resistance specs to make sure it's not off. Did you also verify the fan spins at both low and high speed? If I remember right it should have two powers and two grounds, which controls how fast the motor spins.

Other thing I could think of would be still be air in the system, but that should be out of the system by now. But, that sounds like a fan or air flow problem to me, since when fans went out that is exactly how my car would behave. I would have to take extra long roads with minimal stops to keep my engine from overheating.

 

All good suggestions; just pointing out that it sounds like the OP has a 2004.0 automatic sedan, which has the single clutched fan and not the twin electrics. In which case my suggestion would be to make sure the fan blade itself is on the correct way. There's supposed to be an "F" marking on the front.

 

Do you have hot air blowing from the heater AC with the engine up to temp?

Have you verified the electric fan turns on when the engine is hot?

How far up the gauge does the temp climb? More than halfway?