What are you working on?
For those of you who are considering this mod, it is an easy matter to make your own.
On my Challenger I mounted the relays behind the left front headlights to keep the relays cool, short wires to the battery, and hides them from plain view. On my old Dodge Carry-all I mounted them on the inner fender, next to the battery.
Wiring is simplicity itself: 1: Hot from battery, 2: ground, 3: input from switch (old headlight power wire), 4: output to light (spliced to go to each headlight). One relay for low beams, one for high beams.
I also used relays to power my dual electric fans. Mounted below the horns, short power wire from the alternator output stud, ground, input from temp sender, output to fans.