In your case partly or fully Custom is your only option.
The US 250 has an approx 2" wider sump to gasket face to cater for the almost 4" stroke.
Aussie 250's are closer to 144/170/200 width.
The Australians at High Energy make one #HE 2011that can be welded into your existing sump top if you do it right. Brand new, its 375 Australian dollars.
http://www.highperformanceworld.com.au/ ... low_xc-xe/
The X-flow and non x-flow 250 bottom ends are the same, just a sump depth and pickup change, they just charge you an extra 38%. No point on paying an extra $127 bucks on something you might cut up.
Follow
Mike1157's sump build...you can flitch up a stock sump with Briggs and Stratton gas tanks, and deepen it to a degree. Foxes use a different sump, the x-car 250's will fit in as easy as you please.
Nice choice, by the way, you know what you want, and your going for it. The road blocks (a better sump, weight, axle and trans, bellhousing, marginal stock chain, bigger crank spiggot) allow you to really go nuts with rectifications that fix those things.
Like this.
There is a main cap gidrle too "Ford 250 Main Cap Girdle (stroker/race 6 cyl falcon 4.1 crossflow (x-flow), its based on the 4 LITER DOHC engine.
http://www.ebay.com.au/itm/Ford-250-Mai ... 7064732063
http://i.ebayimg.com/00/s/NjgyWDEyMDU=/ ... ~60_57.JPG