Stop in for a cup of coffee

yeah, swapping isn't an issue.. but just doing research i will need new axles also.. the pre-64 open diff and suregrips used different lengths... also need to get some different 10" backing plates for my drums.. so staying with awesome 2.89 gears for now :) I think the future will be 3.55s
Call Dr. Diff and get some new axles and do the gears before the converter. Can you swap in a 66-67 8 3/4?