So depending on the width of your wheels, you could run:
<TABLE style="WIDTH: 903px; HEIGHT: 55px" border=1 rules=rows cellSpacing=0 width=903 frame=hsides><TBODY><TR bgColor=#cccccc><TD align=left>3782R</TD><TD align=left>P265/40R18</TD><TD align=middle>27X10.50R18</TD><TD align=middle>28</TD><TD align=middle>R2</TD><TD align=middle>9.0-10.0</TD><TD align=middle>9.5</TD><TD align=middle>10.6</TD><TD align=middle>9.6</TD><TD align=middle>26.5</TD><TD align=middle>83</TD><TD align=middle>

</TD><TR bgColor=#ffffff><TD align=left>3785R</TD><TD align=left>P305/35R18</TD><TD align=middle>27X12.50R18</TD><TD align=middle>31</TD><TD align=middle>R2</TD><TD align=middle>10.0-12.0</TD><TD align=middle>11</TD><TD align=middle>12.5</TD><TD align=middle>11.5</TD><TD align=middle>26.4</TD><TD align=middle>83</TD></TR></TBODY></TABLE>
The other options are more than likely too wide unless you have flared out your fenders plus spacers,etc. Even these 305's are probably too wide.
The 265's probably have a wider contact patch than a lot of 275's I'm guessing. Would love to get me some of these!