Tim is spot on,
A 35 Whelen IMP would do anything a 357mag, 357max, 35Rem, 356, 358 or 35Whelen could!! Just cause you would have the HP you don't have to use it until its needed. When its needed, its sure NICE to have!!!
It would be no difference to the smith. Dies are not appreciably any more $$. It would shoot lead loads, my favorite bullet, the Speer 250grain will work at heavy 35 Rem ballistics all the way up to 358 Norma ballistics. A good cast 250-300G bullet would do even better!
Do some reading on these calibers and look at the big picture, keeping in mind if you want bigger later its gonna cost more $$. If you do it now its not appreciably any more $$...
WHAT EVER you choose, there are people here with can help you with recipies and experiences.
CW