There would be three main factors I would consider when determining the best mode of transportation:

$1.$ Distance from supplier: With Kurrat Tools being located in Montreal and their supplier Bradley Metals being in Vancouver, they have a large distance to travel from supplier to seller.

$2.$ Short time frame between ordering and needing product: With only a six$-$week lead time and three of those weeks taken up in production $($assuming no issues$),$ there is not a lot of time to waste in receiving shipment.

$3.$ Size of product: With the item being small precision forgings that aren't overly heavy or large, the amount of room needed for approximately $500$ forgings being delivered per month is not extensive.

Taking all of that into consideration and with the assumption that precision forgings for aircraft producers are costly$.$ The best mode of transportation would be by Air across country with the final to door delivery done by truck.