318 timing mark

So what I have is a 64 valiant that had a 273 and before I had the car my father-in-law put a 318 in it. He used the cover and balancer off the 273. Now I'm looking at do so work to it and I'm wondering if I should change to match the motor. Just wanting to make sure when I go back together I won't have problems dialing the timing in. Next thing will be the rad hose which runs on the driver's side.