Some additional ctr bolt info. most common dia. is 3/8, occasionally 5/16, allways fine thread, common at auto parts stores. Buy one longer than you need so you can use it to compress your spring stack, cut the excess bolt, leave 1/8th ish tail to peen and "lock" the nut, never use a lock washer. You never reuse a ctr bolt, they are stretched. Make sure round bolt head is in receiver hole on X, NOT the nut end. U bolts are also stretched after 1 use. Consider new ones. Most common reason for a repeat ctr bolt break is rust, dirt ect, left between the spring leaves. You tighten the stack, the leaves flex and grind the crud to powder resulting in a loose spring stack that moves and shears the new ctr bolt. Its allways easier to just cut the U-bolts, but be aware of the possibility of things under tension flying. Sometimes fatally!