Ford used two different crossmembers in two different locations to mount the A4LD and T5 in the Fox Mustangs and two different driveshafts to boot, but I can't for the life of me recall which configuration the C3 used.
If you get all of that worked out, then you can focus on the column shifter. If you've ever disconnected the column shift from the
trans and moved it back and forth, you'll notice that there aren't any detents that hold the column shifter in place like a floor shifter has. The column shifter moves smoothly back and forth. That's good news. If you can adapt the column linkage to the A4LD (which I don't think is a problem), you'll be able to operate the transmission. Depending on how much travel you have in the shifter and how much travel it takes to work through the entire shift pattern, you may or may not be able to reach Low 1. No big deal unless you're one of the 1% that actually use it. Your indicator on the dash may be a little off, but I think it's safe to say we all know where the gears are on an automatic.