An easy-ish way to tell is pop in the forks, BotE frames have that higher bottom bracket also and that will show up easily once the chassis is "complete". Also I'm pretty sure that this era Cannondales have a very long but decipherable frame number on the underside of one of the dropouts. Keep an eye on your chainstays by the way, I had a similar frame and it cracked almost the whole way round ... although I was probably a bit tardy in spotting the damage to it.