Yup, you will need to clear coat the decal once dry  in order to enable  it to survive the gasoline. Usually ok with a fine mist coat first, let that flash set and then full clear coat. 

Hello Friends,

thank you for your answers and hints.

Dave no longer make those decals due to low demand.

I attached a picture of my tank, so you can see the status quo.

The "Indian"-lettering is a water decal, the "Scout"-lettering is a vinyl. As you can see, the vinyl decal is hard to patinate. That`s the reason why I prefer a water decal.

It was not possible for me to find the "Scout"-lettering in Europa in water decal form.

At the end my target is to have a tank, which fits visually to the rest of the bike.

All the best from Europe,

Matthias

I haven't bought decals recently, so I don't know much about the providers or if they still are in business, but here you go..

What about http://www.abziehbilderservice.de/ run by Katrin Boehner, The heroic rider and winner in class 1 of the cannonball 2010 across US on a no clutch, single speed, belt driven 1907 JAP?! She said she put down very extensive research on the water decals she makes. 

The link that Tim gave probably advertise decals from classictransfers.

http://www.classictransfers.co.uk/transfer-category/indian/?region=british-us&alphabetical=i-m

Pelders looks like they are still in business https://pelders.nl/

If you want a painted decal, maybe Hans Kreutzen can help.. http://www.paintdoctor.com.au/classic.htm

I think these guys maybe make some water decals, but also distribute from other providers water slide and vinyl transfers.. 

 https://www.heortieg.com/indian-transfers-72-c.asp

Those are all good links Carl-Erik, thanks for posting them!