A turbo off of a geo metro huh? Thats a first for me. It must be
aftermarket turbo setup. It sounds like a T25 turbo is what you would want. On a small intercooler setup I reach full boost around 2.5k rpms and thats running 7psi on my small 2L protege.
You will have to keep in mind that you will have to run pre fuel and I'm not sure how you would go about tuning on a carb engine. Also keep in mind on a crappy tune the motor can pop even at low psi. It really depends on the tune and strenght of your rods.
Edit: Yes I do realise that this is an older post.