Battery tray removal

["David N Waldmann" <dw@vfh.us>]

Mine is pretty well rusted out, what's left of it. However, where it's
attached is still pretty good, so I'm having trouble removing it. I tried a
chisel, but the tendancy is for the footwell metal to pull away from the
tray rather than vice-versa.
 
Any suggestions?
 
-dnw-