I wanted to see how difficult this would be and haven't found a search to answer my question:

I'm interested in taking a 91 Track/Kick 2 door (originally an 8v 3 spd auto) and putting in a 16v from a 93-95 4 door automatic (i.e. all OBDI).  I'd be using everything necessary out of the 4 door for the swap: engine and tranny, wiring harness, instrument cluster, ECM (and tranny ECM).  How will a 4 spd fit into what originally had a 3 spd?  I guess it would be like an X90 with automatic.  What would need to be custom made?  Driveshafts?  Crossmember?  4WD shift lever?

Thanks in advance?

Brian,

I think the 3spd and 4spd autos are the same length so the tcase will stay in the same spot and the 2dr driveshafts should be good to go. I might be wrong, but I'm pretty sure the hole for the tcase shifter is in the same spot for all trannys (manual or autos).

The harness swap will be a PITA ...
There are subtle differences in even the dash/instrument harnesses that may require pins changed (or swap those harnesses too).
I believe the body harness (lights/fuel pump/etc) will mate right up (but that rear defroster won't function ). If the 4dr is going to a scrapper, then I'd cut the body harness plugs in case you need them to swap the ones in the 2dr body.

My books are still packed away, but I have the "supplemental" electrical book for the '91, possibly the same for a '93 (covers the 4dr differences).

P.S. keep the '91 dash 

One more thing bout the harnesses ... your best luck will be if both are from the same plant (CAMI or Japan). Check if the 1st three digits of the VIN match ...

Brian,
I think the 3spd and 4spd autos are the same length so the tcase will stay in the same spot and the 2dr driveshafts should be good to go. I might be wrong, but I'm pretty sure the hole for the tcase shifter is in the same spot for all trannys (manual or autos).

No.  The 3 speed auto and the 5 speed manual are the same lenght.  The 4 speed auto is about 3" longer.  So a front driveshaft from the 4 speed would have to be used, a tcase lever from a tcase that came behind a 4 speed would have to be used, the tcase would have to be mounted farther back, the rear driveshaft would have to be shortened up about 3".