How do u shorten strut housings and what kind of inserts do u use after u shorten them?

Use a large pipe cutter and remove the desired amount from the housing about one inch down from the threads at the top. Carefully weld the pieces back together so the housing is perfectly straight.

Use Tokiko or Koni inserts. I'm sure others will work also.

To determine the amount to remove, take the new insert and place into the housing. Place a piece of masking tape on the insert rod at the housing cap. Lift the insert until it hits the housing cap and place another piece of tape on the rod. Measure the distance between the two peices of tape.

do i get inserts that are made for 280's or do i get them according to the length i remove?

You need to get the inserts first. Some of the inserts such as Konis are a real tight fit so you have to be VERY careful of making sure things are straight when you weld the housing back together.

For Koni inserts or more detailed information, contact True Choice or Ground Control.

Each brand of insert may have a slightly different length.

so do i get ones for the 280z or get ones made for another car with a shorter length and same diameter?

You would be best to contact the folks at the two places I mentioned to find out about what to really get. Because of the dimensions, I think you will need struts made specifically for the Z. I think they are interchangeable between the 240/260/280. If you are looking at doing autoX or simply just street driving you would probably be okay with Tokikos -- they are less expensive than Konis but don't last as long.

Thanks!