What can you tell me about this rearend?

That is a non-sure grip open rear end. You can tell the gear ratio by marking the pinion and case in the same location, then marking on of the ring gear teeth. Rotate the pinion and count how many times it turns to make one full revolution of the ring gear.This will give you an idea. ( 2:76, 3:23, 3:55 etcc..))