Now that I have headers my 02 sensors won’t reach. How do I fix this?

[blkthndr]

This is a common problem when buying aftermarket headers. All aftermarket
headers have much longer primary tubes than the stock manifolds. This means
that the collectors sit much farther downstream than the stock manifolds, thus
usually moving the position for the O2 sensors further away. The stock O2
sensors are 8.5 inches long, and usually the only way to make them fit is to cut
and spice them so that they are longer. However, you can purchase
replacement 3-wire O2 sensors from Bosch that are longer. #13942-8.5” is the
part number for the stock sensor. #13950-13” are 13 inches long and #13953-
16.5” are 16.5 inches long. With Kooks/SCP short tube headers the 16 inch
sensors fit very well.

[SCollord90]

You can also use aftermarket Mustang O2 sensor extensions. They are 4 plugged but they just clip in and you can use the stock/normal O2 sensor. Just call up your local Mustang place and ask. Dallas Mustang Parts has some that you have to cut a little tab off to work but others just clip in.