WITCH DOWN PIPE SHOULD I USE &WHAT SIZE?? WHAT AIR INTAKE IS BEST? INSTALLING LUK SMF CLUTCH KIT THI WEEKEND SHOULD IGET DOWN PIPE FIR ST??

 

I am assuming you have a factory 7.3 IDI turbo.

Without a new outlet flange you can only put a 2.5 inch downpipe on the turbo.
You need to get in touch with ATS to get a new turbo outlet flange for the 3" pipe.
They also are a good place to get the 3" downpipe.

If you are pulling the motor to install the clutch, it would be a great time to fold the body seams over to make room and install the 3" downpipe.