that size get square blade in the 1/4 wide size. i have one and did some 42's and that size was great. one pass per bar. looked great. and hope you have a good shoulder and a few hours. 4 i did took around 1.5 to 2 hours. but i cut the centers to 3 block like the rock crawlers do. helps in the snow for me.
to set blade hight for any worn tire. set blade on head and put head on highes point left and let blade go to lowest point and secure and then heat up and cut. i can send ya a few pics if needed. just qive me email.