i know a c-6 can take tons fo punishment. It will have no problems whatsoever hadleing a 289. I have one and it handles my 428 like nothing and i am well into 500 ft ppunds of torque. The biggest thing is just selecting the right torque converter a properly built c-6 will take anything a 289 can dish out. The best thing i ever did for my car was buy a manule valve body. I got a TCI manule valve boby and my 428 just loved it.
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