If I remember correctly the cast iron 'glides were all the same. The only difference was the adapter plate to make it fit a 6 or an 8. As far as low gear ratios they were the same too. Chevy made up the difference in the rear axle ratios. 8 cylinder passenger cars with a glide used 3.36 and the 6's were either 3.55 or 3.73. Optional ratios were dealer installed at that time and standard shift cars and wagons came with a little deeper gearing than the automatic equipped cars.
Mike
