Which cylinder is the number one on a ford 4.2L?

For the Ford 4.2 liter V6 engine :

If it is a rear wheel drive / 4x4 vehicle :

firewall

3 - 6

2 - 5

1 - 4

front of vehicle

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If it is a front wheel drive vehicle :

firewall

1-----2-----3

4-----5-----6

front of vehicle > driver