Need help picking the right radiator upgrade for my 460 Engine

I have a 1956 Ford f-100 with a 1972 460 ford engine and C-6 tranny.I bought a new 4core radiator from f-100s in arizona thinking that would cool the engine at the present time it over heats and runs out the over flow in about 5 miles.I have had the heads off three times taken to engine builders saying they are fine after mag flux and pressure testing.Same with the intake manifold.I have put a 1/8th inch hole in the thermostat as some told me that would help remove any air pockets.Put new hoses on top and bottom.Fit the stock shroud to fit the five blade flex fan.Checked timing Etc Etc Etc.Ineed to know what it is the pros do with the big blocks to keep them cool????? any help in the area of upgrading for a headache free F-100???????
Bud  

The first thing I would do, is throw away the flex fan, and buy a steel fan like this:
http://www.speedwaymotors.com/Heavy-Duty-Steel-Cooling-Fan,1846.html

Flex fans flatten out, with rpm, so they pull less power. Unfortunately, they also move less air, and can actually block airflow.  I'm not that thrilled with fan clutches, either.  I like to hear the roar of a direct drive fan. That way, I now it's working.
A friend of mine had a 400M with cooling issues.  We couyldn't get the timing nailed down. It would run hot, and bite the starter, or it was a lame dog.  It finally took a distributor, to make it behave.  In the mean time, we tried everything, right down to spring-loaded flaps in the shroud, to let more air throw at highway speed.

I am curious, though.  Does it overheat at idle, or just at highway speed?  
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1949 Chevy 1 1/2ton, home-built hydraulic wrecker.  Rustoleum industrial black, with flames.  Flamethrowers out 5" dual stacks.
1962 Chevy C-20, 402BB, 4-speed, 3.90 positrack. Hauls my camper.... among other things.

Hi PackRatWrecker;
Thanks for your interest in my problem.Yes it over heats setting in the drive way Idling.I just could not believe the stock OEM brand new radiator would not cool this engine.I have been chasing this issue for some time now and notice in the classic truck magazine the proffesional builders seem to always put a new type radiator in the buildup although I have yet to see any reports on what it is they are using,all other information right down to the rubber on the ground..I have been to pomona swap meet several times now and found a 56 like mine with the 460 and he took the complete front clip from the donor car and reconfigured his sheet metal to fit the Lincoln radiator and air conditioning unit.Said he has never had any problems.  

I'm all out of good ideas.  I know a lot of guys that run BBC & BBF, in work trucks, and never fight heating issues.

OTOH, we have a 95 F350(460) at work, that we battle all summer long. Everything but the shortblock has been replaced, at least once.

If I find anything useful, you will see it right here.  
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1949 Chevy 1 1/2ton, home-built hydraulic wrecker.  Rustoleum industrial black, with flames.  Flamethrowers out 5" dual stacks.
1962 Chevy C-20, 402BB, 4-speed, 3.90 positrack. Hauls my camper.... among other things.

Over the decades of similar swap headaches, the No 1 culprit is the radiator cap - fail to seal/maintain pressure/incorrect pressure rating.  The 460 is a modern thin-wall casting so they put heat into the cooling system very quickly.

The No 2 culprit is thermostat - spring fails to operate (seen it)/broken or detatched.