I am planning on making a custom box for my 3rd Gen. It will be about 50-60 pounds when all is said and done. The box will also have compartments for tools, locking of valuables, etc. My plan was to run it over the driver's side rear tire well.

Will this cause enough uneven wear to my tires and shocks to be concerned about?

 

Nah...no more than a person riding in the back seat.

 

Just fill up the cargo pocket on the passenger side to balance everything out and you should be o.k.