Yes, your stud pattern in 5x112. You also need to pay attention to offset (ET) as well. This effects how far the wheel sticks out. The smaller the number, the further it sticks out. My Vancouvers are 7.5 x 18 ET51. I would suspect that your Glendales are about the same. It will be stamped on the back of the wheels somewhere.
In terms of tyres sizes you need to keep the rolling diameter as close to the original as possible. All the following sizes are within acceptable tolerances of each other.
205-55-16
205-50-17
225-45-17
225-40-18
235-35-19
Obviously the smaller you go, the cheaper they will be, but for me aesthetics still play a part in it, so I would be reluctant to go below 17" myself.