Others above are totally correct, if you have a 'deep crank' ring spanner it will aid your work tremendously. As always 'Rule of 9' works but Ford at one time issued a TIB (Technical Information Bulletin) to say they should be adjusted TDC Firing on each cylinder in turn, to be honest and having used both methods there is no difference whatsoever whichever method you use and I have tried with the engine on a bench with a clock gauge on the crank and a DTI on the valves, as long as your on the back of the cam your fine.
