That Corvair battery is a long narrow type that may not be available, today, in any brand. Many Corsair guys use a battery made for Hondas. It fits the narrow space but is not as long as the original battery so it does not have the original appearance. I believe it has substantially more cranking power than the correct type Corsair battery.
I have a Corvair battery (not Delco) that I bought many years ago and only used it to start a car a few times. It might respond to one of the "battery renewal" methods that can be found online. Some Delco stickers, copied from an original battery, might fool the judges next time.
Mike