A/T Tyres on a 90t350

[Johnboy1234]

Hi all, Does anyone have any advice on fitting A/T tyres on a 2003 90t350 RWD? It's a bit of a project! A safari style camper conversion which won't even drive on grass because of the terrible grip it has. I know
It's currently on 21575r16 C with a load rating of 113.
I've found some 22570r16 BFG with a load index of 115 but they are not C rated! I've heard that if they are not commercial rated (C) they might fail a MOT but then others have said as long as the load index is high enough.
Has anybody got any ideas/advice on light truck A/T tyres.
Thanks in advance.