Welcome to ecomodder! It's nice to hear that you AND your husband want to save fuel.
I'll assume you drive much less than your husband. Otherwise some instrumentation for your Trailblazer may save more fuel than your husband's new cam. Of course, driving a Metro will save much more fuel. Some of the math involved in calculating saving was discussed
here.
Also, check out the 100+ hypermiling tips on this site if you haven't done so already.