I'd only ever seen them that way, but all documentation states BO6 is only:

Premier nose.
Premier door trims and armrests.
Complete front floor mat.
55A alternator (not with C60 A/C as it got a bigger alternator anyway).
Utility bumperettes (for cab chassis only to be fitted to Ambulance body).
Belmont hubcaps (HJ-HX), Chrome hubcaps HZ.
Windshield placed into position but not fixed.

I think GMH probably only made them for stock vehicles as column auto, buckets and U17 instruments, however anyone could order one and if you simply chose BO6 on say a HJ cab chassis in December 1974 you'd have got a 173, 3spd, drum brake tonner with a Premier nose and door trims / armrests. Dr Terry has a HZ tonner BO6, it is L31 M41 column auto with U17 instruments and bench seat. My Overlander was the same except buckets. I had a white HZ tonner for a while that was 4.2L, column auto, U17, buckets and A/C. Friends had a HZ tonner in 4.2L, M20.