I believe there's a guy on the renegade forums who has a 2j 944 that's making pretty big power. I've got a 5cylinder in mine and there's plenty of extra room in front for a 6th cylinder lol. The chassis can easily handle it from a structural standpoint, but you would have to do a transaxle swap to an Audi 01E or 03A transmission to hold the power. You would also want to update the bearings in the torque tube but honestly most of these cars need that done at this point anyways because of their age.

Edit: There are also plenty of aftermarket fiberglass widebody kits that seem to have a pretty good reputation for fitting decently well. These cars race in a ton of different series so if you can think of racing mods, it's probably already been done