I only pointed out the Catera V because it's the only one I know of with a manual transmission. I didn't mean you should go and build a V8 Catera. What exactly is wrong with your tranny? It might be rebuildable. Kits cost between $200-$300. My Catera itself had a slipping tranny and lost 4th gear. She now has a used tranny and shifts just fine. My cousin took my old one, rebuilt it, and slapped into his Catera. Our cars use the GM 4L30-E transmission which is also found in:
1991–1995 BMW 525i
1992–1995 BMW 325i
1992–1998 BMW 318i
1994–2001 Honda Passport
1996–1999 BMW 328i
1996–1999 BMW 528i
1996–2000 BMW Z3
1996– Acura SLX
1997–1999 BMW 323i
1999– Isuzu Amigo
2001– Isuzu VehiCROSS
1991–1998 Isuzu Rodeo
1990–2001 Isuzu Trooper
Not sure if their gearing is the same as in the Catera version so some research is needed but the BMW versions are probably a safe bet. As for a "stick" you're on your own. The 4L30E is electronically controlled so the computer will be useless. Don't know what codes would pop up. I guess a RWD GM tranny could be made to fit the chassis but will it mate with the L81 engine in the Catera? Who knows? You'd also need a clutch pedal and master-cylinder. Easiest way, though by no means easy, would be to acquire an Omega pedal box from Great Britain (Vauxhall) or Germany (Opel). If not you'll be cutting and welding. Good Luck.