Dom, I put an explorer 8.8 rear in my 65 street Dart. I found a 3.55 ratio rear with discs. Along with checking the gears, look at the axles for wear where the grease seal rides next to the outer wheel bearing. Also, there can be wear on the pinion seal area. There are repair sleeves to fix this for the pinion, and special bearings that move the seal for the axle problem. Be sure and grab the Metric bolts for the companion flange and also the driveshaft flange if the thing was torched off at the bone yard. That way you might save some $$ for a drive shaft build. The brake lines are similar and if I recall I used two passenger side rubber lines from an 8.8 and a couple of 1/8 steel lines from Auto Zone to hook to the stock Mopar single line from the MC. I would think the Explorer axle tubes are plenty stout, and memory serves me right they are 3 1/4 inch diameter. You might want to weld them to the center section though, just for grins, or if you run slicks.
Be sure and spend the $$ for the best rear you can find, as I didn't, and the repair costs added up real fast.