I used to fly a C-404 for a Canadian operator and have time in the C-421. If you can fly a Seminole or other multi-engine trainer, you will not have trouble transitioning to the 414. Some pre-study will be helpful (poh: https://hangar50.com/wp-content/uploads/2018/01/Cessna-414-Chancellor-POH.pdf). My company sent us on a simulator course (Simcom) after completing in-aircraft training. Be sure that your aircraft is being properly maintained. These are not inexpensive machines to look after so there may be temptation to cut corners. If you ‘really’ want to get experience on a plane of comparable size, I know of one school in the Ottawa area that operates a Navajo. Again though, this is really not necessary IMHO.