Keep in mind..
When mounting a battery in the trunk, that U also need to have a matching gauge ground cable secured cleanly to the frame. Many times we see a heavy gauge wire for the positive lead (+) and a smaller gauge for the negative lead (-). Also the final gauge size depends upon the total amperage load of all connected components including audio, headlights, fuel pump. If <75 Amps #4 cable is OK, if >100 Amps use #2 or #1 cable...

Note that cables and terminals are available from Summit, Jegs or Mancini..

Just my $0.02...