Mal68ibu, No, unfortunately the Grand Prix window regulators will not fit the 64 Chevelle. You could probably use the switches, wiring and motors (maybe), but you would still have to find the correct regulators from another 64-65 "A" body (Buick special, Olds F85, Pontiac tempest, etc).
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Tom Wood
Gold Member #66
502 Powered '66 SS
Some pictures of my '66 under construction;
http://home.attbi.com/~tkmwood55/