Am I an idiot for wanting to boost a high compression 318?

I have experience with boosted applications, what you intend to do is not that crazy, since the boost level target is pretty low (4psi). As insurance or if you experience any pinging (you shouldn't, but if you do first try to take back the ignition timing 1 degree per psi of boost) you can take a couple of precautions: an easy one would be to add methanol injection (boost driven) to increase and another one is to get a set of thicker head gaskets so you can lower your compression easily 8.5 to 9.5 compression should be more than okay and then you can increase boost much more, 8-9 psi with the supercharger or even higher if you go turbo.

Take care,