40 series is a different wheel, it's larger in diameter and wider. It take a tire made for 40 series rims.
If you want a more Monster truck feel, the Pro-line Mashers in the MT and 40 series are a good choice.
Masher MT
40 Series Masher
The Proline Moab is also really nice and has the look of a Interco Super Swamper.
Moab
As far as wheels go, you are kind of limited when using the 23mm hex.
Proline Cheyenne Beadlock
Proline Cheyenne non-beadlock
Proline Commando beadlock