What's involved in installing these conversion bushings? You'll need to remove the standard bushings from the S14/S15 subframe that you're installing. There's a few ways to remove the standard bushings which option you choose is up to you (google is your friend). Once you've got the standard bushings removed you need to press the new bushings in their place. What's the advantage of installing an S14/S15 subframe? The S14/S15 subframe has better geometry than the S13 unit and also offers more track (ie. width). What’s the advantage of these bushings? Besides allowing you to install an S14/S15 rear subframe in your S13, the Polyurethane bushings offer a more solid rear end = better driver control and feel. Do these cause much vibration/noise in the cabin? Not really. Obviously anything more rigid is going to cause an increase in noise and vibration however I'd hardly say that it's noticeable. Chances are if you're installing these you've already got coilovers, your car is lowered, you've got an aftermarket exhaust etc. etc. Do these bushings change the height of the subframe? Yes, they raise the subframe which improves the center of gravity (roll center).