Top anchor bolt nut rusted out

[Tomq]

I don't find any info in the archives on anyone that has tackled the rusted out anchor bolt/nut problem. I was thinking of cutting out the rail on the bottom, that is aluminum I think,replacing the steel plate with a captured nut, then resurfacing the SMC.A problem I see coming is to get the same tolerances regarding hole mounting placement and the fusion of the SMC, to the new construction. Aside from this rust, the cap is pretty good. All or any suggestions welcome,thanks for looking,Tomq