The OZ 380's started in second gear also.

Series I 126's have a relatively low ratio diff and it appears that there are high revs at relatively low speeds.
Series II 126's - 300,s, 420's and 560's got a higher ratio diff which lowered the revs at higher speeds and gave consequently better fuel economy.

If you hold the gear change in the lowest position from rest you will use first gear. You will notice that is verrry low. It will give you a brisk take off before changing into second gear.

This should be referenced in your owners manual.

Australia never received the series I 126 500's. All are private or grey imports.