well :/ unfortunately, wood is kind of a piss poor building material. Its got a terrible strength to weight ratio, it moves with temp/humidity. It will deform under pressure, and your joinery options are limited.
It is cheap, easy to work with, and its weight can be desirable.
but not for a portable table... Metal >>>>>>>>>> wood for anything portable.
I know I am no help, but building a table to hold up 200lbs and resist various lateral force is going to weigh more than you can easily slide out and work with :/ Maybe you put wheels on it so it slides in and out like an ambulance bed... Its going to take up a ton of floor space in your truck though.