66 new yorker, gear ratios

So it's 6am and I wake up thinking about what else...my car.

Just had a thought someone else has probably had. My speedometer is in mph, I'm in Canada so kph is the standard. I've got that extra rear end from the 68..is there a gear set that I can swap in that will in a nutshell make my speedo read in kph or am I needing more coffee?