George, stick with a 1.9/2.0. I would have gone that route if "they" hadn't offered me the 2.4 for what was originally the same money and been perfectly happy till my dyin' day. Keep it simple(yet costly) and just call OGTS and have them send you a rebuilt 2.0 head and block at a cost of about $2500 plus shipping and any extra widgets you want on it. You'll need to swap over stuff like your timing cover, diz, etc. from your existing engine. Then pop a Weber 38 on it and ride off into the sunset.
None of us, even me, has the patience or time to walk you through the process of getting a raised port 2.2/2.4 engine running. If you want to really save money and rebuild what you've got................please don't! None of us has the stomach for 20 newly started threads asking where you can get pistons and rings from.
In case you haven't actually purchased anything from OGTS and gotten on their emailing list, they just sent out a 4th of July sales flyer that list Opel rebuild pistons and stuff. Don't even think about redoing your own head or having dorks at machine shops do it. Everyone who's gone that route recently has had some form of disappointment. $1000 will getcha a big valve, double spring, no cracks, Americanised 2.0 head done by the best people in the country to make one. Get one, put it on, and be done with it.