Fitting size going into bottom of factory TBI lines

[cerial]

I have a 87 TBI 5.7 with dual saddle tanks where someone cut the fuel and return lines before the stainless line.

Been searching and I can't find what the thread is going into these lines. I need the thread size for the feed and return line. This location is down by the frame on the passenger side after the fuel filter.



I have a new tank, inline pre pump filter, walbro pump, post filter, then these lines before the return goes back to the tank.

Going to rebuild the throttle body in the spring and will replace the lines with new factory ones.
But right now I just want to run a fitting into the current lines down by the frame so I don't have to run rubber and clamps.

The last filter has a an-6 fitting so I would like to go an-6 and adapt it right into the stainless line.