83 rusted through to firewall from inside cowl

[slamd83c10]

what can be done, i took the cowl and screen off to clean and do some seam sealer due to a leak in cab, but as i cleaned the old seam sealer out  and started washing it clean i noticed water coming from my firewall right where the seam sealer is, there are some small holes where it has rusted through,, heeeeeeeeeeeeellllllllllllpppppppp....

[Captkaos]

Your only option is to find all the rust, remove it and patch it as best you can.