What I have:
FAST XFI 2.0 EFI controlling cooling fans. The EFI module provides a sink (negative) to ground output signal.
What I am working with:
Cooper Bussman Relay/Fuse module with five fused 35 Amp Relays and an additional 5 constant hot fuses.
The Problem:
The Relay/Fuse box is designed so the relays are triggered with a high/hot +12 volt signal, and the ground side is designed into the negative bus bar.
I think I could make the negative bus bar a positive bus bar and the relays will activate on the low side signal, but I also wanted to use the relays to drive the Low and High Beam head lights which would be high side triggered, so I need a way to invert the signal to the relay trigger?

I know of many way to do this in theory, like using another relay, or a transistor driver circuit, but is there a better / easier way?