Interestingly though, once you get that far back on any of his ancestors, all of a sudden, you see the Arabians back in the mix everywhere, including at least two crosses to the Godolphin Arabian though the stallion Trumpator (b. 1782). Like most Thoroughbreds, Izzy also traces back to Eclipse (b.1764), whose sire line also takes you back to the Darley Arabian (b. 1700) and again to the Godolphin Arabian through his dam. Once you go back that far, there aren't records as those Arabians were desert bred. If you look up Speedy's registry, it only takes two pages before you get to the desert bred horses.
Happy Birthday, my friend!