Hate to bust your bubble but Isuzu is GM. Chevy has a twin of the Isuzu NPR. It's the Chevy W3500. See it here: http://www.chevrolet.com/mediumduty/wseries/w3500/
The Isuzu gas engine is the chevy V8. The 4 cyl diesel is Isuzu. The diesel seem to be low on power with between 140-190 HP. The chevy diesel ver. has a 5.375 rear axle to get the thing moving off the line but you might be limited on a top speed. Diesel fuel econimy might be good even if the fuel costs us .35/gal more. To bad they don't list MPG for medium trucks.
If you plan on driving on the tollway/interstae much you might want to go for a test drive once. See if it gets up to speed fast enough and make sure it will keep up with the other trucks up a slight hill or against the wind (75 MPH here). I been told that other trucks with the Isuzu diesel would not go over 65 mph.
I don't know of any one manufacture of the big three that does not have some problems. No matter what you buy you allways could have some down time.
As far as where it's made it should say on the window sticker. You can't go by manufacture name to say where the vehicle is made. Cars like Hyundhi are now assembled in the US. The new Chevy Cobalt is a Dihatsu and all import.