Yes, I think there is ample photographic evidence of the standard winter sets of TSO BG TSO.
In the days when the mixed ran - or certainly the early era of the mixed, first class was still provided plus the timetable was unbalanced, three up passenger and a freight, two down passenger and the mixed some days/freight on other days and the balance for the stock was added to the evening train from Inverness except on the days when the mixed ran the CK was added to the mixed which (early seventies) still conveyed several parcels vans. The loco balance was, I think the mixed, but often not required if the up freight was not running, freight to Kyle by then being minimal.
From memory I think the vans included one each from Glasgow Salkeld St and from Perth, plus whatever Inverness added and traffic would include mail, parcels, newspapers and I always remember boxes of fresh bakery products from was it Burnetts(?), the then ,major bake in Inverness which could be seen unloaded from the trains at many stations on the north and Kyle lines.
I recall as stated by Gloster above the mixed was booked to precede the early Far North train then shunt at Dingwall to connect but on one occasion when I use it was standing on the Rose St curve when the North train departed and then followed it.
www.strathcarronstation.co.uk
The history tab on this website shows mail/parcels being unloaded across the six foot at Strathcarron (note the point rodding 'trip hazard' down the middle), and I have seen a photo of a non passenger day of the freight/parcels sitting on the opposite 'bang road' platform to unload (an unsignalled move which obviously couldn't happen on the days passengers were conveyed).
The website is advertising Holiday Accommodation in the station buildings. A friend who used Strathcarron in his childhood in the cl37 era was horrified by this whereas I took the view at least the station building is being put to good use rather then falling into disrepair or worse.