its going to be tough to match that size exactly. but 285/75 16's come out to 32.8x11.2 thats kinda close
but go check it out here
http://www.raingler.com/tech/metricTire.asp
keep in mind that actual tire size is never what they say it is. especially offroad tires. i've seen 33x12.5's measure anywhere from 32x11 to 34x14. but thats part of the fun.