The S5 throttle body and TPS is the only bolt on affair. You need the throttle body to get the full range cam. If you're handy, you can make a cam to take the place of the lever arm on the S4 and rework the S4 TPS mount to make it work well as a full range sensor. I've done this and it's worked great. Mentioned to FFE it would be a neat and easy product too.
I've seen a lot of attempts to make it work with other sensors, and very rarely has the execution been worth a damn. That's why I tell everyone to swap the S5 throttle body and TPS.
The sensor Haltech sells now is actually a very nice piece of Bosch material. They're really proud of it too for what they ask for it. The problem everyone runs into trying to fit it, or most any other alternate sensors, if that those sensors typically work on an 8mm D shaped shaft. The RX-7 uses a 10mm shaft with two flats. So you need to turn down the shaft to fit. This invariably gets buggered up.