you're going to exceed the limits of the cobra clutch imo, my buddy has a cobra, clutch got replaced with oem 10k miles before he bought it and the car was stock, now he put 5k miles on it and within the last 1k miles put an exhaust, intake, pulley, and tune and the clutch is starting to slip, he's at rougly 450whp. I dont think it would last long at 500ish hp.
IMO go with a mcleod clutch. doesn't have to be a dual setup, i've heard great things about their new street pro clutches.
as far as fuel, imo go with a single stryker 340 or one of the aeromotive stealth's. that should be sufficient for the first round of mods atleast, then they'll be able to tell you once it's tuned how the duty cycle is and if it'll make it for more or if you'll need a bap.
'03 cobra- KB 2.8 mammoth, midpipe/catback, supporting mods, rxt twin disc, sra w/ 3.73's, E85