Stop in for a cup of coffee

so, hypothetically speaking.

If someone were to get a van and mount tool boxes and make a mini workshop out of it.

how would one know if it is over loaded ......like that is to say that tools and tool boxes weigh a lot and then when gathered in one place, that is going to be a lot weight.

The van in question is a 73 extended 3/4 ton van so what is a "healthy" weight ?