The weight of 400 gallons is approx. 3340 lbs. Also, think about this, when you have a 200 gallon fresh, and 100 gallon black and 100 gallon gray tank, you only have 200 gallons at any given time. You never fill your fresh water tank without dumping your black and/or gray tanks. So, the weight is now approx. 1670 lbs. Not a lot of weight at all. As for weight totals and distribution, the bus is designed to hold well over 10,000 lbs. of luggage, people, etc. We just stripped out well over 1000 lbs. of metal, plastic, insulation, etc. that will be replaced with lighter materials. Also stripped were several thousand pounds of seating, luggage racks and a restroom facility all made of steel and stainless. Also coming out are nearly 1000 pounds of heating pipe, radiator, several industrial blower motors, a very heavy copper condesor which will take 2 men to carry, a very heavy A/C compressor which will also take two men to carry. Even when the conversion is completed, with a full load of 180 gallons of diesel, full freshwater tank, generator, batteries, and my wife and i on board as well as all of our sound gear etc, (no band) the bus will be well underweight. No need to worry about that. Most newer class A RV's have an option to purchase a 10,000 lb. hitch and our bus is much more capable than that. So a 4,000-5,000 lb. vehicle will not be an issue. The hitch will be the limitation in our case. Weight distribution is still being argued by converters everywhere. Most say put the tanks in the rear-most bays to keep the weight of the water over the rear axles. 1670 lbs. of water is a proverbial drop in the bus bucket (no pun intended) but I have also read several NHTSA articles that have hinted these buses over load the rear axle to the point of unloading the front axle and causing the bus to handle unsafely when on slick roads going around turns. So the idea is to add some weight towards the front axles to keep them planted firmly at all times. The engine itself hangs out behind th rear axles and is plenty of weight to unload the front. in any case, our generator will likely end up towards the front of the bus to keep noise and vibration as far away as possible from our bedroom, and the water tanks will go into the middle bays. Anyway, thinking about getting an incinerator toilet that merely burns the defecation into sterile ash. no black tank needed
So we're about to close the sides in with sheetmetal over the next two weeks. We'll see how that goes... as for timelessbeing...ahaha..lol...just because your avatar shows your van up to its belly in muck...doesn't mean we need tracks on our bus lol! 
and phr1$k37, have fully recovered finally...thanks! was a stinker of an injury...but i took it really easy for a month...thanks for the props everyone!