After doing some study on google, here are my conclusions:
The engine was swapped from 1000CC to 1300CC. The E13 engine, which originally came with Nissan Sunny B11, replaced the original B13 1000cc engine. The carburetor may have been part of this E13 engine, or some separate TT (Turbo charged) carb was installed.
I'll need some R&D, and may need posting engine images to seek advice from experts. Btw, there may be some possibility of converting E-series engine to EFI???