A way(cheap deal) I saw was a full frontal picture was taken of the vehicle and in the shot was a graphic scale.
The picture was then projected on to a sheet of drywall and cutout with a sabre saw.
Using an accurate scale , 1 square inch of the drywall material was weighed and then the picture on the drywall with the graphic scale was weighed.
With a little bit of math, there you are.
I trashed the drywall cut out,(it was a Ford EXP and nobody would race one anyway would they ?) and returned the scale, so you are on your own.
