Sounds like you got lucky and got one of the good ones. It seems to be a 50/50 shot of getting a good one. I really haven't read much about them leaking but it wouldn't be a bad idea to check it.
Got a question 4 you about mounting. Are your mounting holes a different spacing on one side to the other? I noticed on my 68 Cuda the pass side mounting bolts are 14" center to center and on the drivers side they are 14-3/4" center to center. The new Champion radiator mounting holes are the same on both sides at 14-3/4" center to center (give or take a smidgen). I had to order a radiator for an early 70's Dart cause my car has been switched to the newer style timing cover and water pump. If the radiator core support changed along with the newer 70's models that might explain the mounting issue with mine. That's easily remedied though. Unlike all the other problems.