Id move weight to the rear, battery(s), fuel cell etc. id out it behind the axle.Id consider a weight box to... I know I know adding weight isnt the best way...but if your not going to be replacing body panels & windows with light weight peices, Id say this is the best choice.
Seen a guy who rigged up a neat set up that allowed him to easily add & remove dumbell weights. he made a contraption bolted to the frame back by the tailgate with 2, foot long threaded bar stock pieces positioned vertically. he would slip th edumbell weights over the rods & had big wing nuts to secure them.