Samsung Galaxy S4, weird model, can I custom ROM? I just got my S4, on a Canadian network. While everyone seems to have I9500, I have the M919V. It's next to impossible to find any useful information on Google regarding this model. Can I use the same custom ROMs as the I9500 users?

There is a way! Read my answer below!
No, since your model number differs - meaning you have a carrier bound device - ROMs meant for standard i9500 devices won't be suited to your device.