If the holes in the frame have been welded up, there's been enough heat stress on the metal that I'd reccomend scrapping it and finding an unmodified frame. Drilling out the welds won't alter the stresses in the metal surrounding the holes. Cracks will probably develop around the drilled-out welds in short order.
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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