I did a lot of investigation into large wheels for the 250 as originally I was going to have air ride (yep I know).
Offset is key. Axe EX20 wheels will fit - you can get them on ebay with et45 offset on 5 x 120.
To get the arches to cap the top of the tyre you'll need to go slightly higher in profile and narrower in width - basically a stretch fit so the tyre wall is pulling in toward the centre line of the wheel. It's a common trick with the ricer etc. crowd.
The reason you need to go up ion profile is you won't be able to close the arch gap otherwise - even with a 60mm drop which is max you can do on coil overs. I think I was looking at 35 profile.
*edit* Just read budget build? - these wheels are a grand a set