is a 65-66 chevelle 12 bolt rear a direct bolt in on a 1965 GTO? any alterations to driveshaft? spring locations? or anything else. I know they both used the narrow rear. I have the stock GTO 10 bolt rear in my car with 3:55 gears. the engine I will be using is just shy of 500 HP. thanks for any info. pinion head.