You can buy a fuse panel(Summit or Jegs) I like them
better than a big ugly factory one... (some guys like
breaker panels but I dont care for them... I like to
be able to see if its blown)... try to get the relays
near the item you are going to run so you dont have
to run alot of length of the heavier wire... most of
my relays are on the passenger firewall where all my
electrical is
EDIT
You do know you have to have a master cut off if
you move the battery to the trunk(just so you know)