HOW DO THEY DO THAT..?

Attention was drawn to Wes White's Trophy Desert Sled, as featured  on CHOP CULT  a while ago.

As the article says, a 1968 Trophy motor, but with a mag ???

Can't figure out how it's been done.

Better pics would be a bonus, but the outer case looks flawless. Even an aftermarket kit would still necessitate major surgery on the crankcase half.