AOA
in my opinion getting a vintage American muscle car in Karachi is a difficult task, these are either dis-mental in shershah or exported to abroad, few are kept by some people like VCCCP after restoration, i suggest you to better search for a toyota crown fourth generation (preferably 2 doors) you could get it in reasonable price all you need some modification / beautification and engine up-gradation with allied accessories
here under are some pictures of Toyota crown and american make vintage muscle cars for compression
thank you