I have an older Bush Hog rotary mower that doesn't have a clutch. Ran over a stump today & it sheared the PTO pin that goes into the Bush Hog gear box. Did what it was designed to do. Can't find a factory pin as my mower is over 30 yrs. old. Bush Hog dealer tells me to use a 3 inch long, three-eighths diameter bolt with a lock-nut. One dealer says to use a Grade 2 bolt, other dealer says to use a Grade 5 bolt. I don't want to damage my tractor's PTO so I'm inclined to go with the weaker Grade 2 Bolt. Any suggestions or advice? Thanx!