Thanks Mark,you can use any 1.4L or larger container that has a bottom and a top port. It does not need to hold any pressure as the overflow tank is not pressurized.
The bottom port gets connected to the hose from the radiator. The top port gets connected to a tube that goes to the belly of the car - this is the overflow tube.
There are many of these types of containers in JEGS or on ebay.
try these auctions:
200101159931 (top feed, which is nice... they achive the bottom feed right thru the cap just like your stock tank does today)
170103836939 this one is nice because it has a screw top. You will need to drill and tap for another fitting for the feedline on the bottom (or near the bottom)
There's a lot more of them out there. If you get stuck, let me know and I will help you out. There is NO reason to move the battery, that is expensive, time consuming and unless you're speed racer on a single, there is no reason to do it.
Check these links:
I mounted mine on my firewall - but I'm singled. It really doesn't matter where you put it so long as you have the tubing arrangement as I mentioned.
Okay i'm about to save all you guys ALOT of trouble and give you one of the easiest and CHEAPEST ways of doing this.
Go read post #28 by Steve Theodore and look at his attatched pictures. The overflow bottle from a new Civic Si will be the answer. Its under $10. Done now close this thread. LoL j/k.