A few years ago I battled a cooling issue with my Charger and I went through the same process as you. Long story short scale/rust/crud in the block broke loose and lodged in the radiator cooling tubes, which limited flow through the radiator. I had the radiator rodded and I put in a tefba filter which solved the problem. I was surprised how much crud it captured. I talked to Gus (fourgearsavoy) a week back and he recently had a similar experience - he put in a filter and trapped a bunch of crud. If all else fails, have the radiator rodded and put in a filter (at least temporarily). twocents

1968 Charger R/T, 440 Auto, GG1;
1969 Super Bee, 383, 4-speed, T5;
1969.5 Road Runner, 440-6, 4-speed, 96;
1970 Duster 340, 4-speed, EV2;
1970 Charger R/T SE, 440 (496), Auto, EB3;
1970 Dart Swinger 340 (416), 4-speed, EV2;
1970 Corvette coupe, LS5, 4-speed, Daytona yellow;
2000 Corvette coupe, LS1, 6-speed, Twin Turbo, Torch red.