backofthepack

I am trying to restore an early edition Fisher CR-7 and am hoping to find someone either with one or who has some background with them. (I tried contacting Trek to see if there were any Fisher old-timers still around, but didn't even get a FOAD response from them.) The frame that I found was mutilated by someone along the line, specifically, where the seat stays bolt to the top tube, someone had run a 1/4 bolt & nut through. I know that there should be two separate bolts and what my plan is to to fill in where the hole was ovalized, and then have helicoils set into the top tube to accept the proper bolts. The only bits of knowledge I am missing are the details of the original bolts: what size/thread were they and what grade bolts should be used (due to their being a structural connection I am guessing that they need to be pretty strong in shear).

Thanks for any helpful advice!