Sue I know your zone 3 so harbin might be the best option but what are you planning to graft to them? I’m assuming some of these varities https://www.ag.ndsu.edu/trees/handbook/th-3-91.pdf. @Lucky_P once upon a time got pears from a nursery on harbin. I’m putting Asian pears on harbin this year but that’s a very different situation. Harbin get very large with euro pears on them and can get decline. You might look at this old thread Rootstock for Ure, Golden Spice and Early Gold pear. My understanding is areas with bad psylla problems are at risk for decline. Hopefully someone from that area can answer the psylla question or give some tips but if I remember correctly psylla are a big problem there. @jerry63 may be of help Pear for 3b -4a . This is a nursery in Carlton, MN you could call (218) 391-1113 to find out more information about pear rootstocks but I suspect they use harbin http://theappletreeguy.com/product-cat/pears/. @Windfall_rob may be another good person to ask if new pear releases have came out. @jessica4b may be aware of cold hardy pear disease issues. @warmwxrules & @northof53 will have some great advise as they can speak from experience on cold tolerant pears that they grow.