I'd reccommend drilling/reaming the rivet holes and using Allen head shoulder bolts and Nylock nuts to secure the spring mount to the frame. As I'm sure you know, drill bits do not make perfectly round, nor accurate-diameter holes. Any slop at all between the spring mount and the frame is too much. Use tapered punches to position the bracket to the frame, and clamp it tight while you're drilling/reaming. Victor Machinery Exchange has chucking reamers in stock at affordable prices.

www.victornet.com

Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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