I plan on doing an engine swap later when my farm truck that holds a 351W dies. In the mean time, I am starting at the back on this build up. That means the rear diff.
Right now, I don't think I will get the performance from a 8.8 3.08 as I would from say a 9" 31 spline T/L 3.90 once I put the built 351 in there.
There are some other factors in my decision also. I need to do a rear brake job and replace the seals right now. Then I have to add that freakin $30 a bottle fluid to the diff after I change the seals.
Instead of repairing the rear and since I need to consider gear change for the future, I am trying to decide the best course of action now. I am trying to minimize my expenses and increase the value of my decisions.
So, a future power increase will require a gear change. Instead of spending money on new drum brakes, why not swap the whole rear end, since I need taller gears anyways and while I'm swapping, why not upgrade to disc?
Does that make sense? I'm planning for the future while addressing today's needs.