I installed Patricks ring and pinion in a Canadian rear end which did require minor modification. The ring gear bolt circle on a Canadian carrier is 6.188" and the bolt circle on U.S. carriers (and Patricks ring gear)is 6.062". Elongating the holes (on your Canadian carrier) 1/16" towards center will make it fit which I did with a 3/8" endmill. The washer spotface is large enough that it requires no modification.
Here's some pictures. I remember that my spiders had a brass/bronze? washer behind them that I saw no mention of in U.S. literature so I suspect these are unique to Canadian rears. Good luck.
