04Fatty.
PJPR01 is correct, those Toyo's are too wide for the RRS and rims so stick with a tyre no wider than 285mm section width dude !
BFGoodrich do their All-Terrain T/A KO in a 285/55R20 size which will sit 32" tall on your 20"x9.5" rims which is the maximum ?
Otherwise it's hard to beat Pirelli Scorpions, but other forum members are having difficulty sourcing these from your resellers.
Most RRS owners are realising the fact it's better to have two sets of tyres/wheels - one for summer and another set for winter.
Cheerio,
Vinniman
'88 Highline
Perth, W.A.