For heavy duty circuits, we have this dual fuse/relay box. Holds 70 amp SPST relays and up to 80 amp fuses.
Add terminals and seals (6 each of Lear MAK 8 for fuses, Delphi Ducon 9.5 for relay contacts, and Delphi Metri-pack 630 18-20 gauge for relay coils) for $20.
Add 2 70-amp relays and 2 fuses for $10.
Type fuse sizes desired in box.