step van conversion load questions

hey every body i am embarking on a wonderful new adventure. i just built a walk in closet in trade for a 78 chevy step van with a spanking new cummins 4bt3.9 and allison 454 tranny and a 14,000 lb rear end it has a beautifully done rv conversion inside and here's my plan. 1st take out the wasted space(too much storage not enough room) then install 2 inch ridgid foam around the area over and behind the rear axle dimension 5Lx5wx2 feet deep. i am a professional stone mason/tile setter of an artistic inclination and i want to build a mobile spa / exibition of my abilities as a 500 dollar a foot contractor. i am putting in a small 2 seat sauna steam bath and running all of this on a woodgas aka syngas generator mounted to the rear bumper (it's super cool stuff). here is where i pass my own ability. how much weight should i (could i) put behind the rear axle. so far i will take out 150lbs of wood and add 3100 lbs of water 350 lbs glass tile 8 gallon potable tank(70lbs) 3(more)deepcycles 150 lbs. so i am estimating at adding 2 tons to this truck and 1.5 has to be on and behind the rear axle.

heres what i am thinking 1st go get semi truck airbags and install rear *if the wieght is too much for good handleing then next move. 2nd install Rockwell tandem axle dual drive with airbags for 1000 dolla this is extreme though i wonder if any one uses a box truck for work and knows if you can safely load 1.5 ton in the tail of this truck. i have more questions too about the airbag install if any body want to give me a quick low down on how to put in or what i actually need to do other than bolt on ie remove springs? add bars i have never worked on a rig like this just bikes and pick ups the truck has an existing blog that i will be keeping up with at chiptruck@blogspot.com check it out thanks everybody

sorry i meant http://chiptruck.blogspot.com/ enjoy

Years ago I carried my race car in the rear of a Grumman stepvan. 1600# over the rear axle and behind it. Never an issue.With this same truck I carried a complete Ford Cortina sticking out the back with a flat towed Cortina attached to the tuck. I had no issues at all. You should be fine with at most adding the airbags.

I would weigh the van as it sits now to see how much it weighs and if possible how much weight is on the back wheels. A scrapyard or truck stop should be able to do this for you. That should tell you how much weight can go on the back wheels. Also, I would leave the tub empty while driving and fill it when you get there. Don't need the water sloshing around while driving.

Another option is to carry some of the stuff on a trailer and then connect it when you get where you are going. Very cool van BTW.

I would build a cover that also has slats attached to it in a grid. The cover would attach securely somehow to the tub. The slats would extend down into the water and be shaped like the reverse of the bottom of the tub. That way the slats will cut down on how much weight can transfer all of a sudden like. Probably don't need a lot of slats, just two going each direction, 90 degrees to each other for a total of 4. Looking straight down on the tub it would look a bit like a tic-tac-toe game if the cover was invisible.

Should be awesome.

OK, five boxes of information and no pictures?

Welcome aboard Trek.