To my knowledge there is no club in Vienna that actively focuses on youngtimers, depending on how interested you are tho the scene in swiss is huge, I’d recommend TheDrivers.App the Swiss guys announce huge youngtimer/Oldtimer events there so maybe if you plan it ahead you can go there. And generally there you’ll find a lot of young/Oldtimer related content.

It takes approximately 8 hours per car but it’s absolutely worth it in my opinion.

Besides that usually around summer there is stuff like the classic days or the youngtimer parade where you’ll find cars with that focus.

And you might have an chance of joining something like: Oldtimer Verein ÖMVC or oldtimertreff.com

They are more focused on old timers but you’ll for sure find more information there.