i want extra cooling compacity for my 7.3 diesel in my f350 box truck. ive been looking at 4 row radiators. what is better a downflow or crossflow and i guess aluminum is better than brass and copper

 

Never heard of the stock setup being inadequate. If you are running hot be advised the thermostat needs to be from International or Ford and there is a check ball in the neck. Make sure it hasn't been left out and that it is free. Lastly, make darn sure you have DCA (diesel cooling additive) aka SCA (supplimental cooling additive) to avoid cavitation holes in your block.

On edit: I assumed you have an older IDI diesel. Powerstrokes are different. You may want to repost in the appropriate diesel engine page.

 

where is check ball and where do i get a diesel cooling additive

 

The check ball is in the thermostat housing close to the thermostat. If you look at the end that bolts to the block there is a hole where the ball is. It might be rusted in place. If the ball falls out there is a fix that I used. I used a brass nut off of a compression fitting that was just slighty larger than the hole. I filed the edges till it could be pressed into the hole and not fall out. Just make sure the ball is loose enough to move around in the hole. Next the thermostat. Make sure the thermostat is a FORD or IH thermostat. I tried thermostats from ADVANCE and NAPA. They DO NOT WORK. The diesel cooling additive I buy from NAPA. I think it is pink in color.

 

What he says and make sure your fan clutch is OK.