I have a 94 z28 a4 car that I’m going to be swapping a TH400 and I need to know what I need to make it work besides the obvious. I have a MWC 9”, torque, arm and crossmember on order, plus a madman dipstick. I know I need a shifter too, but what else do I need to make it work? Tuning, vss etc.Thanks

 

one of the things you need...is the search bar.
There's lots of th400 swaps documented here that have loads of great writeups/pictures/info for you to use.

The basics are simple
-crossmember
-driveshaft
-converter/flexplate combo to work with your engine
-cooler lines
-shifter
-vss setup
-wiring (either for transbrake, or if auto vb still, the passing gear switch)

 

What I really need to know about is how to make my Speedo work and how it affects the tune. Also, what about the shifter wiring?

 

WELL your neural safty is in console, You can actually use the stock shifter just 2 will be 1, 3 will be 2 and OD will be D.
Late model 400s had a reluctor gear you can but them only but they do need ot be installed during build and of course you will need the speed sensor and plug for it wires in the same then someone that can set the count in tune, The speedo should no affect the tune otherwise.
Assuming short tail you will need yoke , driveshaft about 3 inches longer .
Hope this helps , changing the plus per mile is easy enough finding someone with the cable and software willing to do it well a bit harder depending on whre you are.