I suggest making a set of set up bearings for the pinion shaft , You can use the old ones you have for that and use a new set on the new pinion gear
The set up bearings inner race will need to be honed out with a small cylinder hone or a flapper wheel on a small dremil bit, your choice
They need to be loose enough to slide on with very little pressure, not sloppy loose though This will allow you to experiment with the shims to get it set up dead nuts , Same thing on the carrier bearings inner races also if your reusing a older Dana 60
As already mention a good mag base and dial indicator with a accurate inch lb. torque wrench are needed, buy yourself a complete Dodge or Plymouth factory service manual, 1966 to 1971, and read the Dana 60 rear end section thoroughly so you under stand exactly what you need to do to get the pinion depth and the ring gear pattern within tolerances on setting up both the ring gear and the pinion bearing depth and preload along with the backlash and carrier bearing preload as well as getting both(coast and drivepatterns) patterns correct
I have never used a case spreader, I use two pry bars to pry the case out of the housing and a plastic mallet to install it using the carrier bearings as the guide into the carrier bearing seats Using this methods requires you to find out EXACTLY what zero carrier bearing preload shims are needed to achieve that, once you have that then you need to add from .013 to .017 more shim width to get the proper carrier bearing preload, use what your FSM recommends
Setting up a Dana 60 is like anything new, the first time is usually the hardest