Tyre load ratings

I posted this as a follow up on another thread, but thought I'd put it in another subject so it gets seen a bit more. Hope someone out there has some real knowledge and suggestions on this:

My vehicle plaque ('05 Hilux) doesn't give a tyre load rating. It just says the sum of the load capacities of tyres fitted to an axle or axle group is to be not less than 1255 KG front or 1600 KG rear. Referring to the Cooper website, 800 KG load (half of 1600) requires a 100 load rated tyre.

The manual however says 112/110S. I am guessing this means if your tyre is speed rated S, then 110 load rating is OK, otherwise 112 is required.

No one that I can find makes a 112 or 110S tyre in 31/10.5/15. The BFG is 109S and the Cooper ST is 109Q(below S). The nearest I can find is the Cooper ATR in 265/75/15 which is a bit smaller than the 31 and with a less aggressive tread, so likely to be not as good off road as the BFG or ST.

The local BOB Jane Sales Manager says 'mmm, thats interesting. I reckon the 109Q would be OK, but I can't be certain'.

Haven't spoken to the Toyota agent yet, but don't expect any real knowledge there.

Any tyre experts out there who can help?