pull #1 plug and rotate engine til you feel compression starting to build. then watch timing marks to come up on the balancer. remove cap and see where the rotor is pointing that's number one then follow the firing order.
On most cars the firing order is stamped on the intake manifold. the only thing you will sometimes will find on the distributor cap is the number 1 showing the location of the wire that goes to the number one plug.
They have to be in the firing order.
Is there a picture of distributor cap firing order for 2003 ford f150 4.2 engine
Which engine.
It depends on the firing order of the engine
get a book Run your spark plug wire from the #1 plug to the #1 lug on the distributor cap. Then follow the rest of the firing order going clockwise around the cap.
get a factory cap. its better and is marked and the firing order is on the intake
firing order from spark plug to the distributor cap
18436572
1,3,7,5,8,9,10
18436572
18436572