removing corroded belly pan screws

[Cruiser]

We're about to install a new belly pan. The old pan had corroded around the screws that were holding it onto the frame and was hanging down. The old pan came off, no problem, but the old screws are still in the frame . I assume these need to come out, so as not to abrade the new pan, but I haven't been able to get any of them out. Each screw makes a corroded sandwich of aluminum and steel that won't accept any screwdrivers or pliers and has resisted drilling and a sawzall. Is there a good way to get these out or should I just leave them as is?
Doug

[87MH]

A small handheld 4" grinder might do the trick.

[Cruiser]

Thanks, Dennis, I'll try the grinder.

Doug