Hi Olivier,
The measurements are the same as mine. I've also had a few more thoughts...
1. I'm pretty sure the early cars had the steering wheel rivets/bolts showing and the horn push inset centrally, so I think the one Joe shows is correct for your car. They came with either green/yellow or black badges on the actual push part, I don't know what's correct for your car but would guess at the green/yellow.
2. When I bought my car I also saw the OEM wheel, which was a similar design to the one you have but had an entirely different central boss and horn push. Instead of using a pencil connector through the boss, it had a copper brush, really just a metal strip that you bent to contact the horn ring on the steering column. Basically, it looked nothing like the one you have, so again that makes me think that the one Joe's shown is correct. I think the picture below, scanned from a road test, is the way your wheel used to look.
Brian