You have to change both of them obviously, but what's not so obvious, is that the factory did not put the SAME ratios in both the front and rears. My '61 for example has a 3.90 in the rear and a 3.91 in the front. Look at GM specs through the years and you'll find the same situation on them all.
I hope you don't start to change the whole mess around just because it's "easier". Originality WITH functionality isn't easy, cuz everyone would do it. Like having your cake and eating it, too! I hope you get it to where your satisfied.
