hey man good to see you're wanting something different like us. We'll be going with the 18x8.5 ET 45 and 235/45/18s on our transit connect very soon then we'll have something better to show for it. In the mean time, check these links to get a better understanding of what you can expect. personally, I don't see an issue with your desired numbers as the 235 or 245 tires will technically fit the van with the 18 x 8 or even the 18 x8.5. Anything wider, you may have to use coil overs. Be warned that the 245 is approx 10'' wide while the 235 is approx 9 inches wide. We'll be staying with standard but performance struts and stocks.
check out my on going list of wheels that have fit on the van.
viewtopic.php?f=54&t=84998&start=90#p1760857check these sites also:
wheel-size.com (year/Model TC)
tacomaworld.com (calculator)
and the customwheeloffset for transit connect images.