318 differences ??

Use the original vibration balancer for the engine, then put the 70 and later timing chain cover and water pump on.

Find TDC and make a new mark where the damper lines up on the new marks on the timing chain cover.

Then you're good to go...


PS: While changing the timing chain cover, get rid of the junk single row timing chain and install a good double roller timing chain. Like this one:

http://www.manciniracing.com/edelbrock4.html