I used the rubber loom boot on the passenger side to get through the firewall. It's pretty well accessible from the passenger footwell and from the engine bay.
There are a tonne of places to mount a UHF, it just depends on the type of UHF and your preferences for screwing into plastics, cutting facias, reach and aesthetics
There are a tonne of places to mount a UHF, it just depends on the type of UHF and your preferences for screwing into plastics, cutting facias, reach and aesthetics