Besides the transport issue, you also need to be aware of the parts you can and cannot take back to Ontario due to CWD
https://www.ontario.ca/page/chronic-wasting-disease
Hunting outside of Ontario
Stay up to date on the latest hunting regulations. Detailed regulations related to transporting animal body parts are in Section 4 of Ontario Regulation 666/98.
New regulations came into effect January 1, 2021 to help reduce the risk of CWD coming into Ontario through imported cervid body parts hunted in other provinces, states or territories.
If you hunt cervids out of province, you can only bring back to Ontario:
butchered, deboned and packaged meat
a cleaned skull plate and antlers
tanned hides and capes
finished taxidermy mounts
It’s illegal to bring any other body parts from deer species into Ontario. These rules apply to all members of the deer family, or cervids, which comprise more than 37 species.
All imported parts must be clean of all other tissue and labelled with the:
species name
name and address of the owner
location where the imported parts came from
Not sure what you will be hunting there, but:
If you harvest white tail or mule deer in the Kootenays in MUs 4-1, 4-2, 4-3, 4-4, 4-5, 4-6, 4-7, 4-8, 4-23, 4-24 and 4-25 within one week of harvest the head has to be submitted for compulsory testing.
I will assume your guide will take care of that.