Basically it's the same as the 35 Brown/Whelen then, but with a .338" bullet instead of a .358" bullet?

I have made many 338-06 rifles in my years as a gunsmith. I also helped a friend do an "improved" 338-06 and we ran tests on it when it was done.

To be very honest, the gains were very small, and not worth the price of custom dies and a custom ground chamber reamer ,as well as the powder and bullets to fireform the shells.
The standard 338-06 was a far better way to go, in my humble opinion.

Just my 2 cents worth......................