Fuel carrying capacity?
over 47.000 US Gallons / approx. 320.000 lbs (prototype configuration only) in 11 tanks.
Problem is; looking at the artists conception in post 32, passenger cabin windows are shown extending back to where the fuselage tank is located. You can either have useful range or carry cargo/passengers. The only space left is actually in the weapons bay, located between the engine inlet ducts.
The original design depended on the use of a a toxic fuel (zip fuel). But when that was dropped, most of the remaining fuselage space was converted to fuel tankage to carry JP-6.