Running Projects targeting older SDK's

This is related to an earlier question

but since I have no replies, and it IS important, decided I need to reframe the question.

I am trying to compile a much older project which needs the 061 build of openframeworks
Downloaded the archived project to the 061 openframeworks addons directory, but when I try and compile notice it is targeting an older (10.5) SDK as well.
So under
Build Settings>Architectures> Base SDK switched from the missing SDK to the installed Latest OSX 10.11 SDK.
Closed Xcode, reopened and tried recompiling the application.

But STILL get the SAME error message.
There is no SDK with the name or path… MacOSX10.5.sdk

I understand I may still need to source and install an older SDK but my question is
Where ELSE in my Xcode settings would it be referencing this older SDK?