The most obvious difference is the length of the shifter bases - the 90 shifter is on top, 91-94 on bottom. Here you can also see that the mounting holes (circled in pink) are closer together on the 90 shifter base, and the cable mounting points (circled in red) are also closer together on the 90 shifter base.

Here you see the shifter base mounting holes are smaller on the 90 base (on the left). The metal grommets and rubber bushings for the mounting bolts are consequently different sizes, which is why you have to let Dave Symborski know what year your car is when ordering his metal grommet kits.

The 90 shifter - note that the shifter handle is tubular steel welded to a cast steel pivot. The gear selector arm (at bottom of pic) is also cast steel.

The 91-94 shifter - note that the shifter handle is tubular steel welded to a plate steel pivot. The gear selector arm (at bottom of pic) is also plate steel. While it's not fully evident comparing this pic with the one above, the selector arm on the 91-94 is longer than the 90.

The bottom half of the shifter arms - the 91-94 is on the left, 90 on the right. Notice that the 91-94 is much taller above its pivot point.

The shifter handles - 90 stock on left, 91-94 stock in the middle, shortened 91-94 on the right. Note that the 91-94s are longer under the pivot point. The ratio of the top half to bottom half (measured from the center of the pivot) is larger on the 90 shifters, so 91-94s already have a shorter throw than 90s. This is one of many reasons to get a Mofugas short shifter if you own a 90 - it will greatly decrease shifter throws.

Another view of the bottom half of the shifter arm - 90 on the left, 91-94 on the right. Note how the 90 is much narrower than the 91-94 (this is a key point in the install of a Mofugas shifter). Note also that the 90 bottom half has 2 machined surfaces on it - this are the bumpstops to limit the front-to-rear handle movement (The Mofugas short shifter also has the bumpstops on the bottom half). The 91-94 uses the shifter base as the bumpstops.

The bolts the shifter arms pivot on in the shifter base - this is a key point for the install of a Mofugas short shifter in a 1G. Note that the shank of the 91-94 bolt (top) is very small compared to the 90 (bottom). Mofugas has made nylon bushings to fit the 91-94 shifters, but the pivot bushing will not fit on the huge 90 bolt (the mods necessary to install the Mofugas short shifter on a 90 are covered in the Mofugas Shifter VFAQ).

Here is a 90 tranny, with the shifter cable mounting bracket circled. Note the angle between the bolt holes that the shifter cables bolt to, and the bolts that hold it to the tranny.

Here is a 92 tranny, with the shifter cable mounting bracket circled. Note that there is no angle between the bolt holes that the shifter cables bolt to, and the bolts that hold it to the tranny, they are parallel.

A closeup of the brackets, the 90 on the left, 92 on the right.

If you put a 91-up tranny into a 90 car, you'll need to use the 90 mounting bracket, or the tranny will only go into 3/4/5/R, 1/2 won't be accessible. Conversely, if you use a 90 tranny in a 91-94 TEL or GVR4 without swapping the brackets, 1/2/3/4 will work, but you won't be able to access 5/R.

That's it for now. I'll try to get more tranny differences posted later.