My 46 from years of the cab being bounced around developed cracks around where the rear spring bolts let the cab flex, if the springs weren't there than the shock to the cab would break the plates where the spring bolts are mounted. I welded the cracks up and reinforced it with 1/8 steel around where the cracks were. I would get under with a good light and just take a look to make sure theres no wear through where the bolts mount. I still have my cab on a dolly on its back and can send you a picture to show what I mean if you wish.
Bob T
