I think it is great that you are going to pull new copper wires. I would pull a #10 ground and #8 thhn copper conductors (H-H-N) with the conductors so you will have a 4 wire feed. This way conduit size won't be a problem and you will have smaller wire and 50 amp capability. I'm assuming here that you live in an area where metal conduit is required.
What size breaker do you have in your panel for this circuit? I couldn't find any kitchen aid free standing ranges that required more than a 40 amp branch circuit. Need your model# to be sure.
For your information here is the link to new model Kitchen aid range installation instructions. I'm not sure what model you have or if it is new or not. Make sure the bonding jumper is removed from the neutral terminal of the new range. Kitchen aid calls it the ground link.