Greetings and Welcome!
My van started out life as a 15 passenger van. 15 x 150lbs each = 2250lbs. Me, my camper conversion, and everything I own weigh in at under 1000lbs, so I figure I'm good. BUT... I didn't do any of stupid heavy wood conversions either. I would guess that the majority of those heavy wood conversions are way overweight. I bought a passenger van, took out the rear seats, and kept the floor/walls/ceiling intact, so that saved me a ton of extra weight. All my furniture combined likely weighs less than the heavy original seats that I removed.
Keep all of your additions as low as possible to maintain the lowest center of gravity as possible. Adding weight up high or on the roof can huge negative effect on the drivabilty of your van. My cargo van with solar panels on top drove like crap after I added them, and my gas mileage went down big time too. I have nothing above the bottom window line now.
Cheers & keep us posted!