My answers below in Blue:
1: Dump value; do they make a dump value that works on gray and the black or will i need separate values.
A "combination" dump valve is pretty much the standard. It will have two gate-valves so that you can dump the black water first, and follow up with the grey water to help rinse the system.
2: Best place to purchase new tanks with a reduce cost?
For the black tank, it all depends on whether you are going with a "new" configuration, or whether you want it to fit exaclty in the place where the old one sat. If the latter, then the tank was probably made by INCA Plastics, which is still in business, and still has the molds for many of those vintage tanks. Their prices may not be the "best," but they will the be best for what you are looking for. For the grey water tanks, it depends on your design. Vintage Trailer Supply sells some tanks that are designed to fit inside the frame rails so that you don't see anything hanging down below the bellypan. For their volume, they are relatively expensive, compared to "off the shelf" tanks that will definitely hang below your frame. Do a google search from outside the forums for terms like "airforums grey tank" and you should get a bunch of threads talking about layout of grey tanks and suppliers.
3. Can the toilet be located away from the black tank and router just like a house septic system?
The "standard" setup is to have the toilet located immediately above the tank, and the dump valve directly off of that tank. There is just too much opportunity have clogs if you are trying to move black water around in low angle pipes. If you are dead set on flowing black water around, you might look into a marine style macerating toilet. Again, a google search from outside the forums should get you some threads: "airforums macerating toilet".
One other recommendation I would have is if you are relatively computer savvy, and have the patience to learn, download a free copy of SketchUp 3D modeling software. Using this, you can lay out your entire plumbing system in 3D. I have been using it to design my cabinetry, and have found it quite useful in revealing what goes where and what will clash with what. Plus, if you end up ordering tanks with custom spun on fittings (ie., from Vintage TRailer Supply), you will need to know exactly where those fittings need to be (ie., where are the inputs, the outlets, and the vents located).