A friend was having similar slow roll problems with his bucket seat and console car. There is a lot of fine gauge wire in the ignition switch circuit, especially when it has to run out through the neutral safety switch and back. He had heavy gauge battery cables made up and replaced all the ignition switch wires with 12 gauge and had no more problem. Our big block cars have bench seat and the neutral safety switch on the column. I've never had a slow roll problem with any of them. Lucky? Maybe. We have some aluminum faced high heat cloth that we have wrapped starters and solenoids with. So far we haven't had any slow roll problems with them either. Lucky? Maybe.
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Chevelleless after 46 years......but we did find a low mileage, six speed, silver 2005 Corvette. It will just have to do for now.