no offense but had to comment, Quality costs $$ and Glen Ray IMO is unequalled. I went through a fiasco several years back on a customer's 22" equipped R/T that cost me more time and money than I wanted to total up. And you guessed it, it was a heating issue.
All temp measurements were being taken with a laboratory grade digital meter and type k thermocouple's
New core from a local shop that does outstanding work (but he skipped the chapter on thermal efficiency of cores),
freshly rebuilt motor,
block check - negative,
Water pump- negative
Pulley ratios- Stock
Fan - Stock
Restricted exhaust - negative
Have heads rechecked by another shop- negative
Pull engine, remove freeze plugs, find 2 or 3 inside block. AH HAH! Remove errant plugs, reinstall motor, NO Change
Pull engine again send to other shop, complete teardown / rebuild again, sonic check bores (only.030 but?) reinstall and Same Sh-t
Finally call Glen Ray, he listens to my sob story, says send me the radiator if it does not fix your issue, I will fly down to assist. If we can' resolve the issue, you owe me NOTHING! OK, Your on and I'll take that bet.
2weeks or so later the radiator is reinstalled and POOF!!!! the heating issue is GONE!
That was about 10 years ago and per the owner it has never gone above 190 under any conditions including parades on 95 degree day etc.
I can't remember the cost of Glen ray's radiator but If I had paid 10 or 20X I would have been way ahead $$ wise
He has since done a few other "problem" vehicles with the same success

BTW: The owner later told me the problem had plagued the car since he owned it (~15 years)