87-93 front sub under a 66 mustang?

Sure, almost anything is possible, if you have the time, skills and equipment.

I think in one of the mustang rags they put in a macpherson strut front end. Can't remember if it was Mustang Monthly or what.

It does involve cutting and welding on both frames so do your research and be careful.

Edit: It would be a lot easier to just get a performance handling kit from a mustang vendor.