Depends on what trans you are going to use. Gear up and then back down at the rear is never a good thing, before large driveshafts and high torque engines it was the only way.
If your going to re-power a modern trans makes sense, find parts for an odd-ball obsolete trans, while broke down under a load is no fun.
There used to be a guy on here out in Colorado that ran a modern Spicer 6X4 set up with a twin counter-shaft main and aux. He loved it, but was a lot of work and finding parts was difficult.
I ran a 3406B with an RT0 14615 and found 4:11's good on 20" rubber< actualy mine were two spd rear 4.11 and IIRC 5.63 in low. More gears then needed but always one for the job!
If I had more money then sense I would have selected a non-OD trans and rears to make the best use of it.
Gearing up and than back down puts a lot of energy into heat in the boxes that could be used to move the vehicle.