JeepinPenguin,
I finally took the time to get some pics. First is the windshield washer reservoir, that is just like I said before, just chilling/hanging out and bouncing on the factory battery mount plate. There is a bracket that once held it in along with a "heavy duty" zip tie, both the zip tie broke and the actual reservoir plastic tab broke off, it's still attached to the bracket but not the reservoir.
From "drivers seat" looking forward.
Just sitting and chilling there on the wire harness for the lights/strobes/sirens.
Bracket is still attached to the truck bu the reservoir is not attached to the bracket, and you can see the zip tie just hanging around.
Generic 1 gallon reservoir. OEM washer ppump thats hooked up to just the windshield hose. Rear hose is capped off and just hanging there along with the pigtail for the rear pump. You can get a reservoir just like this or two on ebay, swap the pumps into the new tanks, and re-plumb the water line to the new tanks. Pretty easy and straight forward job. You should have plenty of space in the secondary battery location.
My tiny, itsy bitsy battery, not sure how it ever starts the truck but it seems to be working so far. Replacing it will be fun.
Wire jungle connected to the positive terminal, I know one runs to starter, one runs to alternator and one goes inside the cab of and comes out under front passenger seat.
Looking up the front drivers fender where your washer reservoir is. directly behind the 2 plug connectors is the battery tray. Looks like there might be enough room for 35s in here.
Hope this helps with the windshield washer reservoir relocation.
On a side not, your tires rub from the offset of the pretty rims. When i had 33x12.5s on factory rims, no rub, on aftermarket off-set rims, they rubbed.
Vacuum boost brakes are spongy on these trucks. You can bleed them, it will help.
Also, you are thinking about the BDS 4" lift kit. Did you ever look into a body lift? $400 for 3" lift, you will fit 35s, and absolutely no change to factory suspension geometry. If will also give you enough room to put an auxiliary 11gal tank that 2500 Suburbans have.
Heep on posting pics, and lets see some action shots too!