68 Charger Antenna Installation Help !!

[Mopar Crazy]

I have to drill an antenna hole in my 68 front fender. Looking for any advice  !!
Would a stepdown bit be practical or a round hole saw cutting bit work better ? 
I don't want to indent the fender around the hole.

Thanks MC

[70 sublime]

If you are putting it in the factory location I think there might be some inner structure part of the fender you have to deal with also