Go to the local paint shop(the one the pros use) and ask for 3M fast n firm sealer. Comes in tubes just like silicone. It works great. I used it on the 66 to stop my gutters from continuing to rust out my pillars.
[img] http://www.shop.com/op/~3M_Fast_'N_Firm_Seam_Sealer_1_10_gallon_cartridge-prod-17008686 [/img]
---Mike