Been there, done that. You should be able to get the remanant of the bolt out just as truckernix states. You might also be able to "drive" it out using a small punch to turn the bolt. For a replacement, try the local John Deere dealer. Take one of the good bolts with you. There is a head bolt application, I don't recal the part number or application off the top of my head, that matches the 4 bolts in the #4 main of the 235. That's what I ended up doing with mine, after not being able to come up with a suitable replacement. Not even ARP could help me.
