With a little help from Savannah Buzz, this is what I have done:

I remove the radiator to get rodded out. To my suprise, there was alot of debris in front of the radiator. I took it to a local radiator shop to get rodded out but only to find out it was too corroded for him to work on it. I end up buying aluminum one for now. While waiting for the radiator to be shipped, I switched out all the hoses, clamps and replaced the thermostat with a "Chevy" 180F from Advance Auto. I also cleaned out throttle body, upper intake and the PCV valve which the PCV valve was completely clogged. Installed everything, add a bottle of Water Wetter to the coolant and bleed the system. I have been driving for about a week now with the AC on and everything seems to be fine.

Lets hope this is the end of my overheating....

 

That is good news. Many D1 owners would be surprised if they pulled out that rubber strip and looked down between the radiator and the condenser. Be sure to check your fan clutch when warmed up to be sure it does not freewheel (spin more than one turn by hand when released). Depending on the age of the Disco you might have an OBDII port which would allow you to see temps digitally with a scanner or Ultra Gauge.

As for aluminum vs copper/brass radiator, at 1/3 the price and is not clogged up, seems a good deal. Yes, the plastic tanks may not last as long, but if they last 10 years....

 

Don't forget to also clean the AC condensor. Remember, it's in front of the radiator so gets all the airborne crap first.

 

I removed my AC condenser, opened it up real nice out in front. Jury rigged fans.