The cotton core radiator will loose cooling capacity if you use a Toyota Cotton Core as they simply removed fins. A REAL Cotton Core Radiator has bigger fin material with bigger holes and the cooling capacity is not diminished. The metal is what disipates the heat. Having the existing radiator re-cored by a radiator shop and explaining your problem and wat you want done to the radiator shop deals with that issue. I have yet to see an automotive radiator in an industrial application NOT clog up. Also keeping the corners inside the fan shroud clean is imperitive as you loose 30% of your cooling capacity when the corners are clogged. Like I said and Charlie confirmed, air flow is critical as well and overcoming a poor design is tough.
By the way, the newer Nissans are not going to have the same good results as the old ones due to all their changes I am told.
A cotton core radiator will help ONLY IF the unit is overheating due to radiator clogging. When a cotton core is added you actually loose some 20% cooling effiency, however it does reduce radiator maintenance ie, blowing out the radiator. I think it is most certainly an air flow problem and probably lies in the counterweight design...just like some of the older Toyotas
The Toyota has a real problem with the cooling system design for several reasons.
Air Flow and Radiator Style are the biggest.
The Nissan and TCM both have Nissan Engines, High Volume Fan Blades, and a Large Fin Radiator.
Try changing the radiator to a Cotton Core,
and change the fan blade if one is avaliable. If the muffler obstructs the flow or is too close to the radiator either move it or wrap it. In the old days adding some Wynn's Super Cool to the anti-freeze made a world of difference. They don't make the same product now but the local Wnyy's distributor will know what to use if you contact them.
A poor cooling system design is the issue.
When you start using automotive type components it does not help either.
When I see a lift with holes and slots cut out in an effort to cool a machine down it is very evident the manufacturer has a poor design.
If you can tell me what the unit is that runs cool I can thell you the differences in the two systems.
I am in a northern climate and the Toyotas here have the same problem, I know of several facilities where the local dealer has either drilled holes in the cowl or has cut out squares and riveted vents to try to manage the heat.