I've tried all sorts of arrangements but can't get it and it's very time consuming.

I numbered them but they have now rubbed off.

I took them off the dizzy cap and spark plugs so it's not as easy as matching them up.

3 of the leads are identical in length and are the shortest of the 6.

2 longer leads are almost Identical 1 being only 1cm longer than the other.

1 and the last lead is the longest of the 6.

This is for a Falcon ED btw

shortest leads goes to number three, two, and four, next longest goes to one, next for five, longest for six. Firing order is 153624 and number one is the one in the front right hand corner of the car i think. Some caps have small numbers on them to make it easy. Apart from guess and check, the easiest way is to remove the dizzy cap, roatate the motor to top dead centre, and number one is directly over the rotor button. If the rotor button is at the back of the dizzy, rotate the engine a full 360 degrees so its at the front. Or, put a timing light onto a lead and see if its even close to correct timing. If it is, this thats number one

Thanks, my cap was labelled so I didn't have a problem.

Although cleaning the cap fixed nothing, I'm still having the same problems.