Denting floor board

Switched trannys in 65 Dart to newer 904 going with Bouchillon kickdown cable & Hurst Pro-Matic shifter. Needing to make some room under car for clearance for cables & hook-ups. I've pounded with hammer & bars & have dented, dimpled what ever you want to call it so cable's clear. I need a little more room but I think I've maxed out what I can do with hammer and chisel, is there tool I can rent or get that will have a little more oomph to move the last 1/4 inch under there. I'm getting arm weary :banghead: I'm along the tranny tunnel and it's getting tough. thanks