The US 250 has a specfic 1-3/8" crank spigot, not 1-1/4" (1.248") like the 200.
The Aussie 250 uses the smaller 200 crank spigot, so nothing fits the US 250.
There are two kinds of US timing set.
The early 250 timing set it best, but its still not wonderfull. The crank can have an offset dowel fitted to index the stock early timing chain.
After 1973, the timing was changed, but the 200 and 250 were retarded differently by the use of different timing sets. The later 250 timing set isn't very good.
The 302/5.0 OHV timing set can be usedon the US 250, but its a little work maching the crank.
There is a Diecrest gear drive that is an Australian timing gear set for the Australian tall deck 200 and related Aussie 250. Baldrick used one These are 9.38" deck engines with a smaller US 200 style crank sigot, but with a US style 250 camshaft to crank spacing. It only fits the 1.248" spigot crank.
Even if you turned down the crank, you'd then have to create a special spacer to allow the smaller crank snout to seal agaisnt the block...a very diffcult thing to do.