Off the shelf rear axle assembly: Dana 60 instead of 8 3/4"? Pros/cons?

The weight depends on where it came from Some pickup axles are MUCH heavier than others because of thicker tubes.

Unsprung weight is NEVER an advantage.

Around here, there are PLENTY of Ferd 9" stuff which would be my choice if I was to custom build an axle

MUCH of this opinion is based on the idea of "quick gear swap" + in the case of "trouble" you don't have to mess with it under the car.