What size electric fan?

Well, I got mine today and it doesn't fit. My own fault I guess; I should have measured first. I only have 3 1/2" from the waterpump shaft to the radiator. If the difference was only around 1/2", I could probably make it work, but not with this big of a difference. I don't know what's different about my car that it doesn't fit and fits on others, but it doesn't. I guess I'll either be sending the fan back or selling it.