I've never measured it but think that tank holds about 1.5 to 2 quarts. I use another tank for overflow (
9973 - 13 - The Fan Man ) mounted to fan shroud (sort of visible in 3rd pic below). You'll need that if you use this tank as it isn't designed to run less than full. Both of the hose fittings are near the top of the tank so you wouldn't get full coolant flow if you run it low.
Here are pictures for the cross bar I added between the front spring perches:
Simple and well triangulated. This in addition to a Panhard bar on the rear suspension makes for very sure footed cornering.
You could mount a tank on the cross bar but I think an engine mount works better in my opinion. I like to have some room for air flow behind the radiator fan. Mounting stuff on the cross bar starts to add vertical surfaces closer to the fan. Plus the further forward you go, the lower the tank will need to be to clear the hood. The tank needs to be the highest thing in the cooling system so no air gets trapped.