I had the same problem with my 58 Chevy about 15 years ago. The two upper mounts for the front shocks snapped at seperate times. After the second one snapped again about one month later (but at a different spot than the weld), I had new mounts machined and bolted them on. I have a degree in engineering, and both me and my roommates in college at the time (also engineering students) just figured that it was due to metal fatigue. The truck was and is a completely stock vehicle given to me by my grandfather, who bought it new; so, I KNOW that the suspension was never modified in any way.
