That is a gargantuan tank. If you're planning to go racing with this car, you may want to check with the sanctioning body you'd be racing with, they will likely have a maximum tank size. I don't know too many amateur series where the fire crew is prepared to put out a 40 gallon gasoline fire.
It's really difficult to have a combination street and racing car these days. The roll cage requirements for most series would preclude street use of that car, unless you also want to wear a helmet. It sounds like you are building a nice street car that would be great at track days, but making it into a race car would end its days on the street. If you want to go endurance racing, you'd probably need a modified production car.
There is a NASA class for Factory Five Cobras, but I believe it is only for Challenge cars and is a sprint race series. I'm not sure where the Cobra would fit in any of the current endurance series.
If you do go racing, it is very intense and can take over your life.
Those are all good points. Like I said it's something I was on the fence about, and I think at this point while I'd like more than 15 gallons, I'm not sure taking apart a completely done and functional setup (that will realistically have plenty of range for my use of the car) makes any sense to replace with a used tank in unknown condition. So I'm just going to leave it alone. If my friend had gotten this deal 6 months ago before I bought the tank then it would've been different, but for now we'll just call it good as-is.
*break break*
This weekend I ended up getting a few minutes in the garage to play around with a few things. First one was getting the timing cover and the water pump bolted up to check for fits and clearances. The fit is fine. You need to measure the clearance between the timing gears and the timing cover to make sure that it's between 0.005" and 0.075". It's interesting to me that there's so much range allowed, but I measured around 0.008" on one and 0.015" on the other (there are two lugs you have to check). So that's all good, and it'll be a hair higher than that when I put it together for good since I'll put some RTV on the gasket.
One thing I need to confirm (and am not sure of) is the proper plumbing for the heater. The water pump has two ports on it for the heater (something that other electric water pumps didn't have - one of the reasons for going with Meizere), but I have to find some diagram that shows exactly how I use those ports, the thermostat bypass, and the two coolant ports on the intake manifold. I can't remember how all of that goes together. But, it looks good, and once I get a few more bolts and some RTV I should be able to get that all together, and then put on the oil pan.
I also put the headers on. One thing that I'm not entirely fond of is that the headers are shiny, but I'm going for all black on the rest of the car. However as they run I'm sure they'll patina/discolor and so that'll be less of an issue. But man, they look good.
One other thing I noticed once putting them on was that the brake line going to the rear brakes does end up getting pretty close (2-3") from the headers at the driver's side footwell firewall. Since I'm going with DOT 5.1 with a >500F boiling point I'm not too worried about it, but I had some firesleeve that I put on anyway for good measure.
What's exciting is how many systems are close to being completed. I need to order the driveshaft (plan to do that today) and once I have that completed I can put fluid in the transmission and that's completely done. Now that the headers are on I can put the clutch cable in and that's done. I need to run the fuel hard lines and that's done, and then I just have to rivet a bunch of panels.
I've decided on the intake that I need to have that machined down so that it properly is square to the heads. I've read a bunch of posts that say the gaskets that I have (which Edelbrock recommends) will seal some gaps, but then they start leaking after a year or two even if everything is square. So I probably will go for some different gaskets that seem to last longer. I need to call the machine shops around and see who can help with that, or else I'll be doing
@Zeldman 's cut the intake in two and weld it back together method, which I really would rather not do.
Laurie heads back to work tomorrow, and so my plans for her absence include putting in the driveshaft (assuming it arrives in time), putting fluids in the diff and transmission, running the fuel lines, riveting in panels, and putting on the timing cover, water pump, and oil pan for good assuming the oil pan shows up. We'll see how it all goes.