You can certainly check out my database, www.carseatdata.org, and see what was reported there. I looked, and there were some entries for the Cavalier and infant seats, but none for the 2000 Cavalier Coupe, 2 dr, exactly. There is one entry for the Evenflo On My Way (not Position Right) in a '96 2 dr, and it fits well (no position specified - sorry - my standards are higher now than when I started this database).
Otherwise, the Graco SnugRide fit well, as did the Evenflo Discovery. I often recommend the SnugRide because it is lighter than the OMW, it has a front harness adjuster (so you can keep the harness snug all the time), and comes with a 5 point harness.
But the seat you have may be just fine, assuming that you can get a nice snug fit. The techs you see this weekend may be able to get it in, and then to teach you how to do it. With a lap only belt, you often have to flip over the latchplate (the part with the tongue) to keep it in its locked position. Sometimes you may decide to twist the buckle stalk to make it shorter to get a better installation. Sometimes you need a pool noodle or rolled towel instead of the Position Right base adjuster.
The problem you have with the infant seat hitting the front seats will probably be similar with any infant seat. It will probably be worse with the convertible rear facing when your child outgrows the infant seat. Try putting the handle all the way down, way behind the seat. You don't want to leave it up. You may have to put the infant seat behind the passenger seat, with that seat pushed all the way forward. But try to fit it in the center spot first - it is safest.
Good luck, and if you still have questions after you see the techs this weekend, do come back and ask and ask until things make sense.
Toby, CPS tech
[email protected]
www.carseatdata.org