I've never got to the bottom of the radio reception problem (on AM)
My 260 and 75 have exactly the same unit but the difference is very obvious even in the same location. The 260's fine, the 75 is crap
Both are fine on FM
my mark 2 diesel was very poor- Black olive is fine- the radio antenna to hrw connection is behind the nearside rear pillar trim. I believe the diversity amplifier was deleted as part of project "drive".
a saerch on the 75 and zt owners forum may bring up some suggestions