Can I package my Eclipse extension so the right version is automatically installed?

Is there a way to build an Eclipse Update Site s开发者_如何学Pythono that Eclipse 3.3 will install one version of my plug-in while Eclipse 3.4 will install another version? The feature spec allows for "optional included features" but I can't see how to make them conditional on the version of the target.

Background: I've become responsible for an Eclipse extension that has half a dozen plug-ins which depend on a "support" plug-in, and the support plug-in needs to be one version for Eclipse 3.3 and a different version for Eclipse 3.4/3.5. I currently have two separate features, "extension for 3.3" and "extension for 3.4+" but I'd like to not bother my users with this detail.