OOPS! I misread your post. I turn the engine until the #6 valves are on overlap (exhaust closing, intake opening) and time the distributor to fire #1. One and six come to the top of the stroke at the same time, (companion cylinders) with the camshaft determining which one is ready to fire. Ditto for 2 and 5 and 3 and 4. Sorry about the mistake!
If you don't want to make another turn of the crankshaft, just use #6 as your starting point with the engine in its present position. You can set the initial timing on either cylinder close enough to run.
Jerry