The block has a giant casting mark with the words HD or HC on it.
The big differences are HC and HD are 1.3 and 1.6 liter engines, the HC ones with efi had throttle body facing the driver side of the car (rhd)
It also came as carburettor engine too.
The HD came in G200 and other cars like the applause etc which were built on an entirely different body shell.
Here you go